EMC2302 - Dual RPM-Based PWM Fan Controller Datasheet - SMSC

SMSC EMC2302 DATASHE

PRODUCT FEATURES

EMC2302

Dual RPM-Based PWM Fan Controller

Datasheet

General DescriptionThe EMC2302 is an SMBus compliant fan controller withup to two independently controlled PWM fan drivers.Each fan driver is controlled by a programmablefrequency PWM driver and Fan Speed Control algorithmthat operates in either a closed loop fashion or as adirectly PWM-controlled device.

The closed loop Fan Speed Control algorithm (FSC) hasthe capability to detect aging fans and alert the system.It will likewise detect stalled or locked fans and triggeran interrupt.

Additionally, the EMC2302 offers a clock output so thatmultiple devices may be chained and slaved to thesame clock source for optimal performance in largedistributed systems.

ApplicationsServersProjectorsIndustrial and Networking EquipmentNotebook Computers

FeaturesTwo Programmable Fan Control circuits (EMC2302)— 4-wire fan compatible— High speed PWM (26 kHz)— Low speed PWM (9.5Hz - 2240 Hz)— Optional detection of aging fans— Fan Spin Up Control and Ramp Rate Control— Alert on Fan Stall Watchdog Timer RPM-based fan control algorithm— 0.5% accuracy from 500 RPM to 16k RPM (external

crystal oscillator)— 1% accuracy from 500 RPM to 16k RPM (internal clock)SMBus 2.0 Compliant— SMBus Alert compatibleCLK Pin can provide a clock source output Available in a 10-pin MSOP Lead-free RoHS Compliant package

Block Diagram

SMBus Slave

Protocol

PWM Drivers

SMCLK

SMDATA

Tachometer Limit

Registers

Tach Measurement

CLK

ALERT#Fan Speed Control Algorithm

Fan Speed Control Algorithm

TACH1

TACH2

PWM1

PWM2

ET Revision 1.3 (05-18-11)


Datasheet

Order Number(s):

This product meets the halogen maximum concentration values per IEC61249-2-21

For RoHS compliance and environmental information, please visit www.smsc.com/rohs

ORDERING NUMBER PACKAGE FEATURES

EMC2302-1-AIZL-TR 10-pin MSOP (Lead-free RoHS compliant)

Two RPM-based fan speed control algorithms. SMBus address 0101_110(r/w)

EMC2302-2-AIZL-TR 10-pin MSOP (Lead-free RoHS compliant)

Two RPM-based fan speed control algorithms. SMBus address 0101_111(r/w)

80 ARKAY DRIVE, HAUPPAUGE, NY 11788 (631) 435-6000 or 1 (800) 443-SEMI

Copyright © 2011 SMSC or its subsidiaries. All rights reserved.

Circuit diagrams and other information relating to SMSC products are included as a means of illustrating typical applications. Consequently, complete information sufficient forconstruction purposes is not necessarily given. Although the information has been checked and is believed to be accurate, no responsibility is assumed for inaccuracies. SMSCreserves the right to make changes to specifications and product descriptions at any time without notice. Contact your local SMSC sales office to obtain the latest specificationsbefore placing your product order. The provision of this information does not convey to the purchaser of the described semiconductor devices any licenses under any patentrights or other intellectual property rights of SMSC or others. All sales are expressly conditional on your agreement to the terms and conditions of the most recently datedversion of SMSC's standard Terms of Sale Agreement dated before the date of your order (the "Terms of Sale Agreement"). The product may contain design defects or errorsknown as anomalies which may cause the product's functions to deviate from published specifications. Anomaly sheets are available upon request. SMSC products are notdesigned, intended, authorized or warranted for use in any life support or other application where product failure could cause or contribute to personal injury or severe propertydamage. Any and all such uses without prior written approval of an Officer of SMSC and further testing and/or modification will be fully at the risk of the customer. Copies ofthis document or other SMSC literature, as well as the Terms of Sale Agreement, may be obtained by visiting SMSC’s website at http://www.smsc.com. SMSC is a registeredtrademark of Standard Microsystems Corporation (“SMSC”). Product names and company names are the trademarks of their respective holders.

SMSC DISCLAIMS AND EXCLUDES ANY AND ALL WARRANTIES, INCLUDING WITHOUT LIMITATION ANY AND ALL IMPLIED WARRANTIES OF MERCHANTABILITY,FITNESS FOR A PARTICULAR PURPOSE, TITLE, AND AGAINST INFRINGEMENT AND THE LIKE, AND ANY AND ALL WARRANTIES ARISING FROM ANY COURSEOF DEALING OR USAGE OF TRADE. IN NO EVENT SHALL SMSC BE LIABLE FOR ANY DIRECT, INCIDENTAL, INDIRECT, SPECIAL, PUNITIVE, OR CONSEQUENTIALDAMAGES; OR FOR LOST DATA, PROFITS, SAVINGS OR REVENUES OF ANY KIND; REGARDLESS OF THE FORM OF ACTION, WHETHER BASED ON CONTRACT;TORT; NEGLIGENCE OF SMSC OR OTHERS; STRICT LIABILITY; BREACH OF WARRANTY; OR OTHERWISE; WHETHER OR NOT ANY REMEDY OF BUYER IS HELDTO HAVE FAILED OF ITS ESSENTIAL PURPOSE, AND WHETHER OR NOT SMSC HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGES.

Revision 1.3 (05-18-11) 2 SMSC EMC2302DATASHEET

http://www.smsc.com/index.php?tid=219


Datasheet

Table of Contents

Chapter 1 Pin Description. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

Chapter 2 Electrical Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 92.1 Electrical Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 92.2 SMBus Electrical Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

Chapter 3 Communications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 123.1 System Management Bus Interface Protocol . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

3.1.1 SMBus Start Bit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 123.1.2 SMBus Address and RD / WR Bit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 123.1.3 SMBus Data Bytes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 123.1.4 SMBus ACK and NACK Bits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 123.1.5 SMBus Stop Bit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 133.1.6 SMBus Time-out . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 133.1.7 SMBus and I2C Compliance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

3.2 SMBus Protocols . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 133.2.1 Write Byte . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 133.2.2 Read Byte . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 143.2.3 Send Byte . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 143.2.4 Receive Byte . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 143.2.5 Block Write Protocol . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 143.2.6 Block Read Protocol . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 153.2.7 Alert Response Address . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

Chapter 4 Product Description. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 164.1 Fan Control Modes of Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 164.2 PWM Fan Driver . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 174.3 RPM-based Fan Speed Control Algorithm (FSC). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

4.3.1 Programming the RPM-based Fan Speed Control Algorithm . . . . . . . . . . . . . . . . . . . . . 184.4 Tachometer Measurement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

4.4.1 Stalled Fan . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 184.4.2 Aging Fan or Invalid Drive Detection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19

4.5 CLK Pin. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 194.5.1 External Clock . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 194.5.2 Internal Clock. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19

4.6 Spin Up Routine . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 194.7 Ramp Rate Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 204.8 Watchdog Timer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21

4.8.1 Power Up Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 214.8.2 Continuous Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22

Chapter 5 Register Set . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 235.1 Register Map . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23

5.1.1 Lock Entries. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 255.2 Configuration Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 255.3 Fan Status Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26

5.3.1 Fan Status - 24h . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 265.3.2 Fan Stall Status - 25h . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 275.3.3 Fan Spin Status - 26h . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 275.3.4 Fan Drive Fail Status - 27h . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27

SMSC EMC2302 3 Revision 1.3 (05-18-11)DATASHEET


Datasheet

5.4 Fan Interrupt Enable Register. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 275.5 PWM Configuration Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28

5.5.1 PWM Polarity Config - 2Ah . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 285.5.2 PWM Output Config - 2Bh . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28

5.6 PWM Base Frequency Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 285.7 Fan Setting Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 295.8 PWM Divide Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 305.9 Fan Configuration 1 Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 305.10 Fan Configuration 2 Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 325.11 Gain Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 335.12 Fan Spin Up Configuration Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 345.13 Fan Max Step Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 355.14 Fan Minimum Drive Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 365.15 Valid TACH Count Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 365.16 Fan Drive Fail Band Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 375.17 TACH Target Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 375.18 TACH Reading Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 385.19 Software Lock Register. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 395.20 Product ID Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 395.21 Manufacturer ID Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 405.22 Revision Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40

Chapter 6 Typical Operating Curves. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41

Chapter 7 Package Drawing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 437.1 EMC2302 Package Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 437.2 Package Markings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44

Chapter 8 Datasheet Revision History . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45



Datasheet


List of FiguresFigure 1.1 EMC2302 Pin Diagram (10-Pin MSOP) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7Figure 3.1 SMBus Timing Diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12Figure 4.1 System Diagram of EMC2302 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16Figure 4.2 Spin Up Routine . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20Figure 4.3 Ramp Rate Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21Figure 7.1 EMC2302 Package Drawing - 10-Pin MSOP. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43Figure 7.2 EMC2302 Package Markings. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44


Datasheet


List of TablesTable 1.1 Pin Description for EMC2302 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7Table 1.2 Pin Types. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8Table 2.1 Absolute Maximum Ratings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9Table 2.2 Electrical Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9Table 2.3 SMBus Electrical Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10Table 3.1 Protocol Format . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13Table 3.2 Write Byte Protocol . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13Table 3.3 Read Byte Protocol . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14Table 3.4 Send Byte Protocol . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14Table 3.5 Receive Byte Protocol . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14Table 3.6 Block Write Protocol . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14Table 3.7 Block Read Protocol . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15Table 3.8 Alert Response Address Protocol . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15Table 4.1 Fan Controls Active for Operating Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17Table 5.1 EMC2302 Register Set . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23Table 5.2 Configuration Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25Table 5.3 Fan Status Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26Table 5.4 Fan Interrupt Enable Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27Table 5.5 PWM Configuration Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28Table 5.6 PWM Base Frequency Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28Table 5.7 PWM_BASEx[1:0] Bit Decode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29Table 5.8 Fan Driver Setting Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29Table 5.9 PWM Divide Registers. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30Table 5.10 Fan Configuration 1 Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30Table 5.11 Range Decode. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30Table 5.12 Minimum Edges for Fan Rotation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31Table 5.13 Update Time . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31Table 5.14 Fan Configuration 2 Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32Table 5.15 Derivative Options . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32Table 5.16 Error Range Options . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33Table 5.17 Gain Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33Table 5.18 Gain Decode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33Table 5.19 Fan Spin Up Configuration Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34Table 5.20 DRIVE_FAIL_CNT[1:0] Bit Decode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34Table 5.21 Spin Level . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35Table 5.22 Spin Time. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35Table 5.23 Fan Max Step Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35Table 5.24 Minimum Fan Drive Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36Table 5.25 Valid TACH Count Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36Table 5.26 Fan Drive Fail Band Registers. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37Table 5.27 TACH Target Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37Table 5.28 TACH Reading Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38Table 5.29 Software Lock Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39Table 5.30 Product ID Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39Table 5.31 Manufacturer ID Register. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40Table 5.32 Revision Register. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40Table 8.1 Customer Revision History . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45


Datasheet

Chapter 1 Pin Description

Figure 1.1 EMC2302 Pin Diagram (10-Pin MSOP)

Table 1.1 Pin Description for EMC2302

PIN NUMBER PIN NAME PIN FUNCTION PIN TYPE

1 SMDATA SMBus data input/output - requires external pull-up resistor DIOD (5V)

2 SMCLK SMBus clock input - requires external pull-up resistor DI (5V)

3 VDD Power Supply Power

4 GND Ground Power

5 PWM1Push-Pull PWM output driver for Fan 1 DO

Open Drain PWM output driver for Fan 1 OD (5V)

6 TACH1 Open drain tachometer input for Fan 1- requires pull-up resistor DI (5V)

7 PWM2Push-Pull PWM output driver for Fan 2 DO

Open Drain PWM output driver for Fan 2 OD (5V)

8 TACH2 Open drain tachometer input for Fan 2 - requires pull-up resistor DI (5V)

EMC2302 10-MSOP

1

2

3

10

9

8VDD

SMCLK

PWM1

SMDATA

CLK

GND

TACH1

PWM2

TACH2

ALERT#

4

5

7

6



Datasheet

The pin types are described in detail below. All pins labeled with (5V) are 5V tolerant.

APPLICATION NOTE: For the 5V tolerant pins that have a pull-up resistor, the voltage difference between VDD andthe 5V tolerant pad must never be more than 3.6V.

9 CLK

Clock input for tachometer measurement DI (5V)

Push Pull Clock output to other fan controllers to synchronize Fan Speed

ControlDO

10 ALERT# Active low interrupt - requires external pull-up resistor. OD (5V)

Table 1.2 Pin Types

PIN TYPE DESCRIPTION

Power This pin is used to supply power or ground to the device.

DI Digital Input - this pin is used as a digital input. This pin is 5V tolerant.

DO Push / Pull Digital Output - this pin is used as a digital output. It can both source and sink current.

DIODDigital Input / Open Drain Output this pin is used as a digital I/O. When it is used as an output, it is open drain and requires a pull-up resistor. This pin is 5V tolerant.

ODOpen Drain Digital Output - this pin is used as a digital output. It is open drain and requires a pull-up resistor. This pin is 5V tolerant.

Table 1.1 Pin Description for EMC2302 (continued)

PIN NUMBER PIN NAME PIN FUNCTION PIN TYPE



Datasheet

Chapter 2 Electrical Specifications

Note: Stresses above those listed could cause permanent damage to the device. This is a stressrating only and functional operation of the device at any other condition above those indicatedin the operation sections of this specification is not implied.

Note 2.1 For the 5V tolerant pins that have a pull-up resistor, the pull-up voltage must not exceed3.6V when the EMC2302 is unpowered.

2.1 Electrical Specifications

Table 2.1 Absolute Maximum Ratings

Voltage on 5V tolerant pins (V5VT_pin) -0.3 to 5.5 V

Voltage on 5V tolerant pins (|V5VT_pin - VDD|) (see Note 2.1) 0 to 3.6 V

Voltage on VDD pin -0.3 to 4 V

Voltage on any other pin to GND -0.3 to VDD + 0.3 V

Package Thermal Restance - Junction to Ambient (θJA) 132 °C/W

Operating Ambient Temperature Range -40 to 125 °C

Storage Temperature Range -55 to 150 °C

ESD Rating, All Pins, HBM 2000 V

Table 2.2 Electrical Specifications

VDD = 3V to 3.6V, TA = -40°C to 125°C, all Typical values at TA = 27°C unless otherwise noted.

CHARACTERISTIC SYMBOL MIN TYP MAX UNIT CONDITIONS

DC Power

Supply Voltage VDD 3 3.3 3.6 V

Supply Current IDD 400 550 uA

PWM Fan Driver

PWM Resolution PWM 256 Steps

PWM Duty Cycle DUTY 0 100 %

RPM-based Fan Controller

Tachometer Range TACH 480 16000 RPM

Tachometer Setting Accuracy

ΔTACH ±0.5 ±1 % External oscillator 32.768kHz

ΔTACH ±1 ±2 % Internal Oscillator

Input High Voltage VIH 2.0 V



Datasheet

Note 2.2 All voltages are relative to ground.

2.2 SMBus Electrical Specifications

Input Low Voltage VIL 0.8 V

Output High Voltage VOHVDD -

0.4 V 8 mA current drive

Output Low Voltage VOL 0.4 V 8 mA current sink

Leakage currentILEAK ±5 uA

ALERT# pinPowered and unpowered0°C < TA < 85°Cpull-up voltage < 3.6V

Table 2.3 SMBus Electrical Specifications

VDD= 3V to 3.6V, TA = -40°C to 125°C Typical values are at TA = 27°C unless otherwise noted.

CHARACTERISTIC SYMBOL MIN TYP MAX UNITS CONDITIONS

SMBus Interface

Input High Voltage VIH 2.0 V

Input Low Voltage VIL 0.8 V

Output High Voltage VOHVDD - 0.4 V

Output Low Voltage VOL 0.4 V 4 mA current sink

Input High/Low Current IIH / IIL ±5 uA Powered and unpowered0°C < TA < 85°C

Input Capacitance CIN 5 pF

SMBus Timing

Clock Frequency fSMB 10 400 kHz

Spike Suppression tSP 50 ns

Bus free time Start to Stop tBUF 1.3 us

Setup Time: Start tSU:STA 0.6 us

Setup Time: Stop tSU:STP 0.6 us

Data Hold Time tHD:DAT 0 us

Data Setup Time tSU:DAT 0.6 us

Table 2.2 Electrical Specifications (continued)

VDD = 3V to 3.6V, TA = -40°C to 125°C, all Typical values at TA = 27°C unless otherwise noted.

CHARACTERISTIC SYMBOL MIN TYP MAX UNIT CONDITIONS



Datasheet

Clock Low Period tLOW 1.3 us

Clock High Period tHIGH 0.6 us

Clock/Data Fall time tFALL 300 ns Min = 20+0.1CLOAD ns

Clock/Data Rise time tRISE 300 ns Min = 20+0.1CLOAD ns

Capacitive Load CLOAD 400 pF per bus line

Table 2.3 SMBus Electrical Specifications (continued)

VDD= 3V to 3.6V, TA = -40°C to 125°C Typical values are at TA = 27°C unless otherwise noted.

CHARACTERISTIC SYMBOL MIN TYP MAX UNITS CONDITIONS



Datasheet

Chapter 3 Communications

3.1 System Management Bus Interface ProtocolThe EMC2302 communicates with a host controller, such as an SMSC SIO, through the SMBus. TheSMBus is a two-wire serial communication protocol between a computer host and its peripheraldevices. A detailed timing diagram is shown in Figure 3.1. Stretching of the SMCLK signal is supported;however, the EMC2302 will not stretch the clock signal.

3.1.1 SMBus Start Bit

The SMBus Start bit is defined as a transition of the SMBus Data line from a logic ‘1’ state to a logic‘0’ state while the SMBus Clock line is in a logic ‘1’ state.

3.1.2 SMBus Address and RD / WR Bit

The SMBus Address Byte consists of the 7-bit client address followed by a RD / WR indicator bit. Ifthis RD / WR bit is a logic ‘0’, then the SMBus Host is writing data to the client device. If this RD / WRbit is a logic ‘1’, then the SMBus Host is reading data from the client device.

The EMC2302-1 SMBus address is set at 0101_110(r/w)b.

The EMC2302-2 SMBus address is set at 0101_111(r/w)b.

3.1.3 SMBus Data Bytes

All SMBus Data bytes are sent most significant bit first and composed of 8-bits of information.

3.1.4 SMBus ACK and NACK Bits

The SMBus client will acknowledge all data bytes that it receives (as well as the client address if itmatches and the ARA address if the ALERT# pin is asserted). This is done by the client device pullingthe SMBus Data line low after the 8th bit of each byte that is transmitted.

The Host will NACK (not acknowledge) the data received from the client by holding the SMBus dataline high after the 8th data bit has been sent.

Figure 3.1 SMBus Timing Diagram

SMDATA

SMCLK

TLOW

TRISE

THIGH

TFALL

TBUF

THD:STA

P S S - Start Condition P - Stop Condition

THD:DAT TSU:DATTSU:STA

THD:STA

P

TSU:STO

S



Datasheet

3.1.5 SMBus Stop Bit

The SMBus Stop bit is defined as a transition of the SMBus Data line from a logic ‘0’ state to a logic‘1’ state while the SMBus clock line is in a logic ‘1’ state. When the EMC2302 detects an SMBus Stopbit has been communicating with the SMBus protocol, it will reset its client interface and prepare toreceive further communications.

3.1.6 SMBus Time-out

The EMC2302 includes an SMBus timeout feature. Following a 30ms period of inactivity on theSMBus, the device will time-out and reset the SMBus interface.

The SMBus timeout feature is disabled by default and can be enabled via clearing the DIS_TO bit inthe Configuration register (20h).

3.1.7 SMBus and I2C Compliance

The major difference between SMBus and I2C devices is highlighted here. For complete complianceinformation refer to the SMBus 2.0 specification.

1. Minimum frequency for SMBus communications is 10kHz (I2C has no minimum frequency).

2. The slave protocol will reset if the clock is held low for longer than 30ms (I2C has no timeout).

3. The slave protocol will reset if both the clock and data lines are held high for longer than 150us.

4. I2C devices do not support the Alert Response Address functionality (which is optional for SMBus).

5. The Block Read and Block Write protocols are only compliant with I2C data formatting. They donot support SMBus formatting for Block Read and Block Write protocols.

3.2 SMBus Protocols The EMC2302 is SMBus 2.0 compatible and supports Send Byte, Read Byte, Receive Byte and WriteByte as valid protocols as shown below. It will respond to the Alert Response Address protocol but isnot in full compliance.

All of the below protocols use the convention in Table 3.1. When reading the protocol blocks, the valueof YYYY_YYYb should be replaced with the respective SMBus addresses.

3.2.1 Write Byte

The Write Byte is used to write one byte of data to the registers as shown below Table 3.2.

Table 3.1 Protocol Format

DATA SENT TO DEVICE

DATA SENT TO THE HOST

# of bits sent # of bits sent

Table 3.2 Write Byte Protocol

STARTSLAVE

ADDRESS WR ACKREGISTER ADDRESS ACK

REGISTER DATA ACK STOP

1 -> 0 YYYY_YYYb 0 0 XXh 0 XXh 0 0 -> 1



Datasheet

3.2.2 Read Byte

The Read Byte protocol is used to read one byte of data from the registers as shown in Table 3.3.

3.2.3 Send Byte

The Send Byte protocol is used to set the internal address register pointer to the correct addresslocation. No data is transferred during the Send Byte protocol as shown in Table 3.4.

3.2.4 Receive Byte

The Receive Byte protocol is used to read data from a register when the internal register addresspointer is known to be at the right location (e.g. set via Send Byte). This is used for consecutive readsof the same register as shown in Table 3.5.

3.2.5 Block Write Protocol

The Block Write is used to write multiple data bytes to a group of contiguous registers as shown inTable 3.6. It is an extension of the Write Byte Protocol.

Table 3.3 Read Byte Protocol

START SLAVE ADDRESS

WR ACK Register Address

ACK START Slave Address

RD ACK Register Data

NACK STOP

1 -> 0 YYYY_YYYb 0 0 XXh 0 0 -> 1 YYYY_YYYb 1 0 XXh 1 0 -> 1

Table 3.4 Send Byte Protocol

STARTSLAVE

ADDRESS WR ACKREGISTER ADDRESS ACK STOP

1 -> 0 YYYY_YYYb 0 0 XXh 0 0 -> 1

Table 3.5 Receive Byte Protocol

STARTSLAVE

ADDRESS RD ACK REGISTER DATA NACK STOP

1 -> 0 YYYY_YYYb 1 0 XXh 1 0 -> 1

Table 3.6 Block Write Protocol

STARTSLAVE

ADDRESS WR ACKREGISTER ADDRESS ACK

REGISTER DATA ACK

1 ->0 YYYY_YYYb 0 0 XXh 0 XXh 0

REGISTER DATA ACK

REGISTER DATA ACK . . .

REGISTER DATA ACK STOP

XXh 0 XXh 0 . . . XXh 0 0 -> 1



Datasheet

START REGISTER DATA

1->0 Y XXh

ACK STOP

0 0 -> 1

3.2.6 Block Read Protocol

The Block Read is used to read multiple data bytes from a group of contiguous registers as shown inTable 3.7. It is an extension of the Read Byte Protocol.

3.2.7 Alert Response Address

The ALERT# output can be used as a processor interrupt or as an SMBus Alert when configured tooperate as an interrupt.

When it detects that the ALERT# pin is asserted, the host will send the Alert Response Address (ARA)to the general address of 0001_100xb. All devices with active interrupts will respond with their clientaddress as shown in Table 3.8.

The EMC2302 will respond to the ARA in the following way if the ALERT# pin is asserted.

1. Send Slave Address and verify that full slave address was sent (i.e. the SMBus communicationfrom the device was not prematurely stopped due to a bus contention event).

2. Set the MASK bit to clear the ALERT# pin.

Table 3.7 Block Read Protocol

SLAVE ADDRESS

WR ACK REGISTER ADDRESS

ACK START SLAVE ADDRESS

RD ACK

YYY_YYYb 0 0 XXh 0 1 ->0 YYYY_YYYb 1 0

REGISTER DATA

ACK REGISTER DATA

ACK REGISTER DATA

ACK . . . REGISTER DATA

NACK

XXh 0 XXh 0 XXh 0 . . . XXh 1

Table 3.8 Alert Response Address Protocol

START

ALERT RESPONSE ADDRESS RD ACK

DEVICE ADDRESS NACK STOP

1 -> 0 0001_100b 1 0 YYYY_YYYb 1 0 -> 1



Datasheet

Chapter 4 Product Description

The EMC2302 is an SMBus compliant fan controller with two programmable frequency PWM fandrivers. The fan drivers can be operated using two modes: the RPM-based Fan Speed ControlAlgorithm or the direct fan drive setting.

Figure 4.1 shows a system diagram of the EMC2302.

4.1 Fan Control Modes of OperationThe EMC2302 has two modes of operation for each fan driver. Each mode of operation uses the RampRate control and Spin Up Routine.

1. Direct Setting Mode - in this mode of operation, the user directly controls the fan drive setting.Updating the Fan Driver Setting Register (see Section 5.7) will instantly update the PWM fan drive.Ramp Rate control is optional and enabled via the EN_RRC bits.

Whenever the Direct Setting Mode is enabled, the current drive will be changed to what was last written into the Fan Driver Setting Register.

2. Fan Speed Control Mode (FSC) - in this mode of operation, the user determines a targettachometer count and the PWM drive setting is automatically updated to achieve this target speed.The algorithm uses the Spin Up Routine and has user definable ramp rate controls.

This mode is enabled setting the EN_ALGO bit in the Fan Configuration Register.

Figure 4.1 System Diagram of EMC2302

EMC2302

SMCLK

SMDATA

ALERT#

VDD

3.3V

MCU

TACH1tachometer

PWM1Drive Circuit

TACH2tachometer

PWM2Drive Circuit

32.768KHz Clock Input or Output

CLK

GND



Datasheet

4.2 PWM Fan DriverThe EMC2302 supports 2 PWM output drivers. Each output driver can be configured to operate as anopen-drain (default) or push-pull driver and each driver can be configured with normal or inversepolarity. Additionally, the PWM frequencies are independently programmable with ranges from 9.5Hzto 26kHz in four programmable frequency bands.

4.3 RPM-based Fan Speed Control Algorithm (FSC)The EMC2302 includes 2 RPM-based Fan Speed Control Algorithms. Each algorithm operatesindependently and controls a separate fan driver. Each algorithm is controlled manually (by setting thetarget fan speed).

This fan control algorithm uses Proportional, Integral, and Derivative terms to automatically approachand maintain the system’s desired fan speed to an accuracy directly proportional to the accuracy ofthe clock source.

The desired tachometer count is set by the user inputting the desired number of 32.768kHz cycles thatoccur per fan revolution. This is done by manually setting the TACH Target Register. The user maychange the target count at any time. The user may also set the target count to FFh in order to disablethe fan driver for lower current operation.

For example, if a desired RPM rate for a 2-pole fan is 3000 RPMs, then the user would input thehexidecimal equivalent of 1296 (51h in the TACH Target Register). This number represents the numberof 32.768KHz cycles that would occur during the time it takes the fan to complete a single revolutionwhen it is spinning at 3000RPMs.

Table 4.1 Fan Controls Active for Operating Mode

DIRECT SETTING MODE FSC MODE

Fan Driver Setting (read / write) Fan Driver Setting (read only)

EDGES[1:0] EDGES[1:0] (Fan Configuration)

- RANGE[1:0](Fan Configuration)

UPDATE[2:0] (Fan Configuration)

UPDATE[2:0] (Fan Configuration)

LEVEL(Spin Up Configuration)

LEVEL(Spin Up Configuration)

SPINUP_TIME[1:0] (Spin Up Configuration)

SPINUP_TIME[1:0] (Spin Up Configuration)

Fan Step Fan Step

- Fan Minimum Drive

Valid TACH Count Valid TACH Count

- TACH Target (read / write)

TACH Reading TACH Reading

- DRIVE_FAIL_CNT[1:0] and Drive Band Fail Registers



Datasheet

The EMC2302’s RPM-based Fan Speed Control Algorithm has programmable configuration settingsfor parameters such as ramp-rate control and spin up conditions. The fan driver automatically detectsand attempts to alleviate a stalled/stuck fan condition while also asserting the ALERT# pin. TheEMC2302 works with fans that operate up to 16,000 RPMs and provide a valid tachometer signal.

The fan controller will function either with an externally supplied 32.768kHz clock source or with it’sown internal 32kHz oscillator depending on the required accuracy. The EMC2302 offers a clock outputthat enables additional devices to be slaved to the same clock source.

4.3.1 Programming the RPM-based Fan Speed Control Algorithm

The RPM-based Fan Speed Control Algorithm is disabled upon device power up. The followingregisters control the algorithm. The EMC2302 fan control registers are pre-loaded with defaults thatwill work for a wide variety of fans so only the TACH Target Register is required to set a fan speed.The other fan control registers can be used to fine-tune the algorithm behavior based on applicationrequirements.

Note that steps 1 - 6 are optional and need only be performed if the default settings do not providethe desired fan response.

1. Set the Spin Up Configuration Register to the Spin Up Level and Spin Time desired.

2. Set the Fan Step Register to the desired step size.

3. Set the Fan Minimum Drive Register to the minimum drive value that will maintain fan operation.

4. Set the Update Time and Edges options in the Fan Configuration Register.

5. Set the Valid TACH Count Register to the highest tach count that indicates the fan is spinning.Refer to AN17.4 RPM to TACH Counts Conversion for examples and tables for supported RPMranges (500, 1k, 2k, 4k).

6. Set the TACH Target Register to the desired tachometer count.

7. Enable the RPM-based Fan Speed Control Algorithm by setting the EN_ALGO bit.

4.4 Tachometer MeasurementThe tachometer measurement circuitry is used in conjunction with the RPM-based Fan Speed ControlAlgorithm to update the fan driver output. Additionally, it can be used in Direct Setting mode as adiagnostic for host based fan control.

This method monitors the TACHx signal in real time. It constantly updates the tachometermeasurement by reporting the number of clocks between a user programmed number of edges on theTACHx signal (see Table 5.12).

The tachometer measurement provides fast response times for the RPM-based Fan Speed ControlAlgorithm and the data is presented as a count value that represents the fan RPM period.

APPLICATION NOTE: The tachometer measurement method works independently of the drive settings. If thedevice is put into Direct Setting and the fan drive is set at a level that is lower than the fancan operate (including zero drive), then the tachometer measurement may signal a StalledFan condition and assert an interrupt.

4.4.1 Stalled Fan

A Stalled fan is detected if the tach counter exceeds the user-programmable Valid TACH Count setting.If a stall is detected, the device will flag the fan as stalled and trigger an interrupt.

If the RPM-based Fan Speed Control Algorithm is enabled, the algorithm will automatically attempt torestart the fan until it detects a valid tachometer level or is disabled.



Datasheet

The FAN_STALL Status bit indicates that a stalled fan was detected. This bit is checked conditionallydepending on the mode of operation.

Whenever the Direct Setting Mode or the Spin Up Routine is enabled, the FAN_STALL interrupt will be masked for the duration of the programmed Spin Up Time (see Table 5.22) to allow the fan to reach a valid speed without generating unnecessary interrupts.

In Direct Setting Mode, whenever the TACH Reading Register value exceeds the Valid TACH Count Register setting, the FAN_STALL status bit will be set.

When using the RPM-based Fan Speed Control Algorithm, the stalled fan condition is checked whenever the Update Time is met and the fan drive setting is updated. It is not a continuous check.

4.4.2 Aging Fan or Invalid Drive Detection

This is useful to detect aging fan conditions (where the fan’s natural maximum speed degrades overtime) or a speed setting that is faster than the fan is capable of. The EMC2302 contains circuitry thatdetects that the programmed fan speed can be reached by the fan. If the target fan speed cannot bereached within a user defined band of tach counts at maximum drive, the DRIVE_FAIL status bits areset and the ALERT# pin is asserted.

4.5 CLK Pin The CLK pin has multiple functionality as determined by the settings of the Configuration register.

4.5.1 External Clock

The EMC2302 allows the user to choose between supplying an external 32.768kHz clock or use ofthe internal 32kHz oscillator to measure the tachometer signal. This clock source is used by the RPM-based Fan Speed Control Algorithm to calculate the current fan speed. This fan controller accuracy isdirectly proportional to the accuracy of the clock source.

When this function is used, the external clock is driven into the device via the CLK pin.

4.5.2 Internal Clock

Alternately, the EMC2302 may be configured to use its internal clock as a clock output to drive otherfan driver devices. When configured to operate in this mode, the device uses its internal clock fortachometer reading and drives the CLK pin using a push-pull driver.

4.6 Spin Up RoutineThe EMC2302 also contains programmable circuitry to control the spin up behavior of the fan driverto ensure proper fan operation.

The Spin Up Routine is initiated in Direct Setting mode when the setting value changes from 00h toanything else.

When the Fan Speed Control Algorithm is enabled, the Spin Up Routine is initiated under the followingconditions:

1. The TACH Target Register value changes from a value of FFh to a value that is less than the ValidTACH Count (see Section 5.15).

2. The RPM-based Fan Speed Control Algorithm’s measured TACH Reading Register value is greaterthan the Valid TACH Count setting.



Datasheet

When the Spin Up Routine is operating, the fan driver is set to full scale (optional) for one quarter ofthe total user defined spin up time. For the remaining spin up time, the fan driver output is set at auser defined level (30% through 65% drive).

After the Spin Up Routine has finished, the EMC2302 measures the TACHx signal. If the measuredTACH Reading Register value is higher than the Valid TACH Count Register setting, the FAN_SPINstatus bit is set and the Spin Up Routine will automatically attempt to restart the fan.

Figure 4.2 shows an example of the Spin Up Routine in response to a programmed fan speed changebased on the first condition above.

4.7 Ramp Rate ControlThe Fan Driver can be configured with automatic ramp rate control. Ramp rate control is accomplishedby adjusting the drive output settings based on the Maximum Fan Step Register settings and theUpdate Time settings.

If the RPM-based Fan Speed Control Algorithm is used, then this ramp rate control is automaticallyused. The user programs a maximum step size for the fan drive setting and an update time. Theupdate time varies from 100ms to 1.6s while the fan drive maximum step can vary from 1 count to 31counts.

When a new fan drive setting is entered, the delta from the next fan drive setting and the previous fandrive setting is determined. If this delta is greater than the Max Step settings, then the fan drive settingis incrementally adjusted every 100ms to 1.6s as determined by the Update Time until the target fandrive setting is reached. See Figure 4.3.

Figure 4.2 Spin Up Routine

100%(optional)

30% through 65%

Algorithm controlled drive

Fan Step

Spin Up Time

¼ of Spin Up Time

Update Time

Target Count Changed

Target Count Reached

New Target Count

Prev Target Count = FFh

Check TACH



Datasheet

4.8 Watchdog TimerThe EMC2302 contains an internal Watchdog Timer for all fan drivers. The Watchdog timer monitorsthe SMBus traffic for signs of activity and works in two different modes based upon device operation.These modes are Power Up Operation and Continuous Operation as described below.

For either mode of operation, if four (4) seconds elapse without activity detected by the host, then thewatchdog will be triggered and the following will occur:

1. The WATCH status bit will be set.

2. The fan driver will be set to full scale drive. It will remain at full scale drive until it is disabled.

3. The ALERT# pin is asserted.

APPLICATION NOTE: When the Watchdog timer is activated, the Fan Speed Control Algorithm is automaticallydisabled. Disabling the Watchdog will not automatically set the fan drive nor re-activate theFan Speed Control Algorithm. This must be done manually.

4.8.1 Power Up Operation

The Watchdog Timer only starts immediately after power-up. Once it has been triggered or deactivated,it will not restart although it can be configured to operate in Continuous operation. While the Watchdogtimer is active, the device will not check for a Stalled Fan condition.

Figure 4.3 Ramp Rate Control

Previous Setting

Next Desired Setting

Max Step

Max Step

Update Time

Update Time

Setting Changed



Datasheet

In the Power Up Operation, the Watchdog Timer is disabled by any of the following actions:

1. Writing the Fan Setting Register will disable the Watchdog Timer.

2. Enabling the RPM-based Fan Speed Control Algorithm by setting the EN_ALGO bit will disable theWatchdog Timer. The fan driver will be set based on the RPM-based Fan Speed Control Algorithm.

Writing any other configuration registers will not disable the Watchdog Timer upon power up.

4.8.2 Continuous Operation

When configured to operate in Continuous Operation, the Watchdog timer will start immediately. Thetimer will be reset by any access (read or write) to the SMBus register set. The four second Watchdogtimer will restart upon completion of SMBus activity.



Datasheet

Chapter 5 Register Set

5.1 Register MapThe following registers are accessible through the SMBus Interface. All register bits marked as ‘-’ willalways read ‘0’. A write to these bits will have no effect.

Table 5.1 EMC2302 Register Set

ADDR R/WREGISTER

NAME FUNCTIONDEFAULT

VALUE LOCK PAGE

Configuration and control

20h R/W Configuration Configures the clocking and watchdog functionality 40h SWL Page 25

24h R-C Fan Status Stores the status bits for the RPM-based Fan Speed Control Algorithm 00h No Page 26

25h R-C Fan Stall Status Stores status bits associated with a stalled fan 00h No Page 26

26h R-C Fan Spin Status Stores status bits associated with a spin-up failure 00h No Page 26

27h R-C Drive Fail Status Stores status bits associated with drive failure 00h No Page 26

29h R/W Fan Interrupt Enable Register

Controls the masking of interrupts on all fan related channels 00h No Page 27

2Ah R/W PWM Polarity Config Configures Polarity of all PWM drivers 00h No Page 28

2Bh R/W PWM Output Config Configures Output type of PWM drivers 00h No Page 28

2Dh R/W PWM Base Frequency

Selects the base frequency for PWM output 2 00h No Page 28

Fan 1 Control Registers

30h R/W Fan 1 Setting

Always displays the most recent fan driver input setting for Fan 1. If the

RPM-based Fan Speed Control Algorithm is disabled, allows direct user

control of the fan driver.

00h No Page 29

31h R/W PWM 1 Divide Stores the divide ratio to set the frequency for Fan 1 01h No Page 30

32h R/W Fan 1 Configuration 1

Sets configuration values for the RPM-based Fan Speed Control Algorithm for

the Fan 1 driver2Bh No Page 30


Sets additional configuration values for the Fan 1 driver 28h SWL Page 32



Datasheet

35h R/W Gain 1Holds the gain terms used by the RPM-based Fan Speed Control Algorithm for

the Fan 1 driver2Ah SWL Page 33

36h R/W Fan 1 Spin Up Configuration

Sets the configuration values for Spin Up Routine of the Fan 1 driver 19h SWL Page 34

37h R/W Fan 1 Max Step Sets the maximum change per update for the Fan 1 driver 10h SWL Page 35

38h R/W Fan 1 Minimum Drive

Sets the minimum drive value for the Fan 1 driver

66h(40%) SWL Page 36

39h R/W Fan 1 Valid TACH Count

Holds the tachometer reading that indicates Fan 1 is spinning properly F5h SWL Page 36

3Ah R/W Fan 1 Drive Fail Band Low Byte Stores the number of Tach counts used

to determine how the actual fan speed must match the target fan speed at full

scale drive

00h SWLPage 37

3Bh R/W Fan 1 Drive Fail Band High Byte 00h SWL

3Ch R/W TACH 1 Target Low Byte

Holds the target tachometer reading low byte for Fan 1 F8h No Page 37

3Dh R/W TACH 1 Target High Byte

Holds the target tachometer reading high byte for Fan 1 FFh No Page 37

3Eh R TACH 1 Reading High Byte

Holds the tachometer reading high byte for Fan 1 FFh No Page 38

3Fh R TACH 1 Reading Low Byte

Holds the tachometer reading low byte for Fan 1 F8h No Page 38

Fan 2 Control Registers

40h R/W Fan 2 Setting

Always displays the most recent fan driver input setting for Fan 2. If the

RPM-based Fan Speed Control Algorithm is disabled, allows direct user

control of the fan driver.

00h No Page 29

41h R/W PWM 2 Divide Stores the divide ratio to set the frequency for Fan 2 01h No Page 30

42h R/W Fan 2 Configuration1

Sets configuration values for the RPM-based Fan Speed Control Algorithm for

Fan 22Bh No Page 30


Sets additional configuration values for the Fan 2 driver 28h SWL Page 32

45h R/W Gain 2Holds the gain terms used by the RPM-based Fan Speed Control Algorithm for

Fan 22Ah SWL Page 33

46h R/W Fan 2 Spin Up Configuration

Sets the configuration values for Spin Up Routine of the Fan 2 driver 19h SWL Page 34

47h R/W Fan 2 Max Step Sets the maximum change per update for Fan 2 10h SWL Page 35

Table 5.1 EMC2302 Register Set (continued)

ADDR R/WREGISTER


VALUE LOCK PAGE



Datasheet

ADDR AULT

20h 0h

During Power-On-Reset (POR), the default values are stored in the registers. A POR is initiated whenpower is first applied to the part and the voltage on the VDD supply surpasses the POR level asspecified in the electrical characteristics. Any reads to undefined registers will return 00h. Writes toundefined registers will not have an effect.

5.1.1 Lock Entries

The Lock Column describes the locking mechanism, if any, used for individual registers. All SWLregisters are Software Locked and therefore made read-only when the LOCK bit is set.

5.2 Configuration Register

48h R/W Fan 2 Minimum Drive

Sets the minimum drive value for the Fan 2 driver

66h(40%) SWL Page 36

49h R/W Fan 2 Valid TACH Count

Holds the tachometer reading that indicates Fan 2 is spinning properly F5h SWL Page 36

4Ah R/W Fan 2 Drive Fail Band Low Byte Stores the number of Tach counts used

to determine how the actual fan speed must match the target fan speed at full

scale drive

00h SWLPage 37

4Bh R/W Fan 2 Drive Fail Band High Byte 00h SWL

4Ch R/W TACH 2 Target Low Byte

Holds the target tachometer setting low byte for Fan 2 F8h No Page 37

4Dh R/W TACH 2 Target High Byte

Holds the target tachometer setting high byte for Fan 2 FFh No Page 37

4Eh R TACH 2 Reading High Byte

Holds the tachometer reading high byte for Fan 2 FFh No Page 38

4Fh R TACH 2 Reading Low Byte

Holds the tachometer reading low byte for Fan 2 F8h No Page 38

Lock Register

EF R/W Software Lock Locks all SWL registers 00h SWL Page 39

Revision Registers

FDh R Product ID Stores the unique Product ID 36h No Page 39

FEh R Manufacturer ID Stores the Manufacturer ID 5Dh No Page 40

FFh R Revision Revision 80h No Page 40

Table 5.2 Configuration Register

R/W REGISTER B7 B6 B5 B4 B3 B2 B1 B0 DEF

R/W Configuration MASK DIS_TO WD_EN - - - DR_EXT_CLK

USE_EXT_CLK

4

Table 5.1 EMC2302 Register Set (continued)

ADDR R/WREGISTER


VALUE LOCK PAGE



Datasheet

ADDR EFAULT

24h 00h

25h 00h

26h 00h

27h 00h

The Configuration Register controls the basic functionality of the EMC2302. The bits are describedbelow. The Configuration Register is software locked.

Bit 7 - MASK - Blocks the ALERT# pin from being asserted.

‘0’ (default) - The ALERT# pin is unmasked. If any bit in the status registers is set, the ALERT# pin will be asserted (unless individually masked via the Fan Interrupt Enable Register).

‘1’ - The ALERT# pin is masked and will not be asserted.

Bit 6 - DIS_TO - Disables the SMBus timeout function for the SMBus client (if enabled).

‘0’ - The SMBus timeout function is enabled.

‘1’ (default) - The SMBus timeout function is disabled allowing the device to be fully I2C compliant.

Bit 5 - WD_EN - Enables the Watchdog timer (see Section 4.8) to operate in Continuous Mode.

‘0’ (default) - The Watchdog timer does not operate continuously. It will function upon power up and at no other time (see Section 4.8.1).

‘1’ - The Watchdog timer operates continuously as described in Section 4.8.2.

Bit 1 - DR_EXT_CLK - Enables the internal tachometer clock to be driven out on the CLK pin so thatmultiple devices can be synced to the same source.

‘0’ (default) - The CLK pin acts as a clock input.

‘1’ - The CLK pin acts as a clock output and is a push-pull driver.

Bit 0 - USE_EXT_CLK - Enables the EMC2302 to use a clock present on the CLK pin as thetachometer clock. If the DR_EXT_CLK bit is set, then this bit is ignored and the device will use theinternal oscillator.

‘0’ (default) - The EMC2302 will use its internal oscillator for all Tachometer measurements.

‘1’ - The EMC2302 will use the oscillator presented on the CLK pin for all Tachometer measurements.

5.3 Fan Status Registers

The Fan Status registers contain the status bits associated with each fan driver.

5.3.1 Fan Status - 24h

The Fan Status register indicates that one or both of the fan drivers has stalled or failed or that theWatchdog Timer has expired (see Section 4.8).

Table 5.3 Fan Status Registers

R/W REGISTER B7 B6 B5 B4 B3 B2 B1 B0 D

R-C Fan Status WATCH - - - - DRIVE_FAIL

FAN_SPIN

FAN_STALL

R-C Fan Stall Status - - - - - - FAN2_

STALLFAN1_ STALL

R-C Fan Spin Status - - - - - - FAN2_

SPINFAN1_ SPIN

R-C Fan Drive Fail Status - - - - - - DRIVE_

FAIL2DRIVE_FAIL1



Datasheet

ADDR FAULT

29h 00h

Bit 7 - WATCH - Indicates that the Watchdog Timer has expired. When set, each fan is driven to 100%duty cycle and will remain at 100% duty cycle until they are programmed. This bit is cleared when itis read.

Bit 2 - DRIVE_FAIL - Indicates that one or both fan drivers cannot meet the programmed fan speedat maximum PWM duty cycle. This bit is set when any bit in the Fan Drive Fail Status register is setand cleared when all bits in the Fan Drive Fail Status register are cleared.

Bit 1 - FAN_SPIN - Indicates that one or both fan drivers cannot spin up. This bit is set when any bitin the Fan Spin Status register is set and cleared when all of the bits in the Fan Spin Status registerare cleared.

Bit 0 - FAN_STALL - Indicates that one or both fan drivers have stalled. This bit is set when any bit inthe Fan Stall Status register is set and cleared when all of the bits in the Fan Stall Status register arecleared.

5.3.2 Fan Stall Status - 25h

The Fan Stall Status register indicates which fan driver has detected a stalled condition (seeSection 4.4.1). All bits are cleared upon a read if the error condition has been removed.

Bit 1 - FAN2_STALL - Indicates that Fan 2 has stalled.

Bit 0 - FAN1_STALL - Indicates that Fan 1 has stalled.

5.3.3 Fan Spin Status - 26h

The Fan Spin Status register indicates which fan driver has failed to spin-up (see Section 4.6). All bitsare cleared upon a read if the error condition has been removed.

Bit 1 - FAN2_SPIN - Indicates that Fan 2 has failed to spin up.

Bit 0 - FAN_SPIN - Indicates that Fan 1 has failed to spin up.

5.3.4 Fan Drive Fail Status - 27h

The Fan Drive Fail Status register indicates which fan driver cannot drive to the programmed speedeven at 100% duty cycle (see Section 4.4.2 and Section 5.12). All bits are cleared upon a read if theerror condition has been removed.

Bit 1 - DRIVE_FAIL2 - Indicates that Fan 2 cannot reach its programmed fan speed even at 100% dutycycle. This may be due to an aging fan or invalid programming.

Bit 0 - DRIVE_FAIL1 - Indicates that Fan 1 cannot reach its programmed fan speed even at 100% dutycycle. This may be due to an aging fan or invalid programming.

5.4 Fan Interrupt Enable Register

The Fan Interrupt Enable controls the masking for each Fan channel. When a channel is enabled, itwill cause the ALERT# pin to be asserted when an error condition is detected.

Table 5.4 Fan Interrupt Enable Register

R/W REGISTER B7 B6 B5 B4 B3 B2 B1 B0 DE

R/WFan

Interrupt Enable

- - - - - - FAN2_INT_EN

FAN1_INT_EN



Datasheet

ADDR DEFAULT

2Ah 00h

2Bh 00h

AD T

2

Bit 1 - FAN2_INT_EN - Allows Fan 2 to assert the ALERT# pin if an error is detected.

Bit 0 - FAN1_INT_EN - Allows Fan 1 to assert the ALERT# pin if an error condition is detected.

‘0’ (default) - An error condition on Fan X will not cause the ALERT# pin to be asserted, however the status registers will be updated normally.

‘1’ - An error condition (Stall, Spin Up, Drive Fail) on Fan X will cause the ALERT# pin to be asserted.

5.5 PWM Configuration Registers

The PWM Config registers control the output type and polarity of all PWM outputs.

5.5.1 PWM Polarity Config - 2Ah

Bit 1 - POLARITY2 - Determines the polarity of PWM 2.

Bit 0 - POLARITY1 - Determines the polarity of PWM 1.

‘0’ (default) - the Polarity of the PWM driver is normal. A drive setting of 00h will cause the output to be set at 0% duty cycle and a drive setting of FFh will cause the output to be set at 100% duty cycle.

‘1’ - The Polarity of the PWM driver is inverted. A drive setting of 00h will cause the output to be set at 100% duty cycle and a drive setting of FFh will cause the output to be set at 0% duty cycle.

5.5.2 PWM Output Config - 2Bh

Bit 1 - PWM2_OT - Determines the output type of PWM 2 driver.

Bit 0 - PWM1_OT - Determines the output type of the PWM 1 driver.

‘0’ (default) - The PWM 1 output is configured as an open drain output.

‘1’ - The PWM 1 output is configured as a push-pull output.

5.6 PWM Base Frequency Register

Table 5.5 PWM Configuration Registers

R/W REGISTER B7 B6 B5 B4 B3 B2 B1 B0

R/W PWM Polarity Config - - - - - - POLARITY

2POLARITY

1

R/W PWM Output Config - - - - - - PWM2_OT PWM1_OT

Table 5.6 PWM Base Frequency Register

DR R/W REGISTER B7 B6 B5 B4 B3 B2 B1 B0 DEFAUL

Dh R/W PWM Base Frequency - - - -

PWM_BASE2_1

PWM_BASE2_0

PWM_BASE1_1

PWM_BASE1_0

00h



Datasheet

The PWM Base Frequency register determines the base frequency that is used with the PWM Divideregister to determine the final PWM frequency. Each PWM frequency is set by the base frequency andits respective divide ratio (see Section 5.8).

Controls the base frequency of PWM drivers 1-3 2

Bits 3-2 - PWM_BASE2[1:0] - Determines the base frequency of the PWM2 driver.

Bits 1-0 - PWM_BASE1[1:0] - Determines the base frequency of the PWM1 driver.

5.7 Fan Setting Registers

The Fan Setting register always displays the current setting of the respective fan driver. Reading fromany of the registers will report the current fan speed setting of the appropriate fan driver regardless ofthe operating mode. Therefore it is possible that reading from this register will not report data that waspreviously written into this register.

While the RPM-based Fan Speed Control Algorithm is active, the register is read only. Writing to theregister will have no effect and the data will not be stored.

The contents of the register represent the weighting of each bit in determining the final output voltage.The output drive for a PWM output is given by Equation [1].

Table 5.7 PWM_BASEx[1:0] Bit Decode

PWM_BASEX[1:0]

BASE FREQUENCY1 0

0 0 26.00kHz (default)

0 1 19.531kHz

1 0 4,882Hz

1 1 2,441Hz

Table 5.8 Fan Driver Setting Registers

ADDR R/W REGISTER B7 B6 B5 B4 B3 B2 B1 B0 DEFAULT

30h R/W Fan 1 Setting 128 64 32 16 8 4 2 1 00h

40h R/W Fan 2 Setting 128 64 32 16 8 4 2 1 00h

[1]Drive VALUE255

---------------------⎝ ⎠⎛ ⎞ 100%×=



Datasheet

5.8 PWM Divide Registers

The PWM Divide registers determine the final frequency of the respective PWM Fan Driver. Each driverbase frequency is divided by the value of the respective PWM Divide Register to determine the finalfrequency. The duty cycle settings are not affected by these settings, only the final frequency of thePWM driver. A value of 00h will be decoded as 01h.

5.9 Fan Configuration 1 Registers

The Fan Configuration 1 registers control the general operation of the RPM-based Fan Speed ControlAlgorithm used for the respective Fan Driver.

Bit 7 - EN_ALGOx - enables the RPM-based Fan Speed Control Algorithm.

‘0’ - (default) the control circuitry is disabled and the fan driver output is determined by the Fan Driver Setting Register.

‘1’ - the control circuitry is enabled and the Fan Driver output will be automatically updated to maintain the programmed fan speed as indicated by the TACH Target Register.

Bits 6- 5 - RANGEx[1:0] - Adjusts the range of reported and programmed tachometer reading values.The RANGE bits determine the weighting of all TACH values (including the Valid TACH Count, TACHTarget, and TACH reading) as shown in Table 5.11.

Table 5.9 PWM Divide Registers


31h R/W Fan 1 Divide 128 64 32 16 8 4 2 1 01h

41h R/W Fan 2 Divide 128 64 32 16 8 4 2 1 01h

Table 5.10 Fan Configuration 1 Registers



EN_ ALGO1 RANGE1[1:0] EDGES1[1:0] UPDATE1[2:0] 2Bh


EN_ ALGO2 RANGE2[1:0] EDGES2[1:0] UPDATE2[2:0] 2Bh

Table 5.11 Range Decode

RANGEX[1:0]REPORTED MINIMUM

RPMTACH COUNT MULTIPLIER1 0

0 0 500 1

0 1 1000 (default) 2

1 0 2000 4

1 1 4000 8



Datasheet

Bits 4-3 - EDGESx[1:0] - determines the minimum number of edges that must be detected on theTACHx signal to determine a single rotation. A typical fan measured 5 edges (for a 2-pole fan). Formore accurate tachometer measurement, the minimum number of edges measured may be increased.

Increasing the number of edges measured with respect to the number of poles of the fan will causethe TACH Reading registers to indicate a fan speed that is higher or lower than the actual speed. Inorder for the FSC Algorithm to operate correctly, the TACH Target must be updated by the user toaccommodate this shift. The Effective Tach Multiplier shown in Table 5.12 is used as a direct multiplierterm that is applied to the Actual RPM to achieve the Reported RPM. It should only be applied if thenumber of edges measured does not match the number of edges expected based on the number ofpoles of the fan (which is fixed for any given fan).

Contact SMSC for recommended settings when using fans with more or less than 2 poles.

Bit 2-0 - UPDATEx[2:0] - determines the base time between fan driver updates. The Update Time,along with the Fan Step Register, is used to control the ramp rate of the drive response to provide acleaner transition of the actual fan operation as the desired fan speed changes. The Update Time isset as shown in Table 5.13.

Table 5.12 Minimum Edges for Fan Rotation

EDGESX[1:0]MINIMUM TACH

EDGES NUMBER OF FAN POLES

EFFECTIVE TACH MULTIPLIER (BASED ON 2

POLE FANS)1 0

0 0 3 1 pole 0.5

0 1 5 2 poles (default) 1

1 0 7 3 poles 1.5

1 1 9 4 poles 2

Table 5.13 Update Time

UPDATEX[2:0]

UPDATE TIME 2 1 0

0 0 0 100ms

0 0 1 200ms

0 1 0 300ms

0 1 1 400ms (default)

1 0 0 500ms

1 0 1 800ms

1 1 0 1200ms

1 1 1 1600ms



Datasheet

ADDR FAULT

33h 28h

43h 28h

5.10 Fan Configuration 2 Registers

The Fan Configuration 2 register control the tachometer measurement and advanced features of theRPM-based Fan Speed Control Algorithm.

Bit 6 - EN_RRCx - Enables ramp rate control when the corresponding fan driver is operated in theDirect Setting Mode.

‘0’ (default) - Ramp rate control is disabled. When the fan driver is operating in Direct Setting mode, the fan setting will instantly transition to the next programmed setting.

‘1’ - Ramp rate control is enabled. When the fan driver is operating in Direct Setting mode, the fan drive setting will follow the ramp rate controls as determined by the Fan Step and Update Time settings. The maximum fan drive setting step is capped at the Fan Step setting and is updated based on the Update Time as given by Table 5.13.

Bit 5 - GLITCH_ENx - Disables the low pass glitch filter that removes high frequency noise injectedon the TACHx pin.

‘0’ - The glitch filter is disabled.

‘1’ (default) - The glitch filter is enabled.

Bits 4 - 3 - DER_OPTx[1:0] - Control some of the advanced options that affect the derivative portionof the RPM-based Fan Speed Control Algorithm as shown in Table 5.15.

Table 5.14 Fan Configuration 2 Registers

R/W REGISTER B7 B6 B5 B4 B3 B2 B1 B0 DE

R/W Fan 1 Configuration 2 - EN_

RRC1GLITCH_

EN1 DER_OPT1 [1:0] ERR_RNG1[1:0] -

R/W Fan 2 Configuration 2 - EN_

RRC2GLITCH_

EN2 DER_OPT2 [1:0] ERR_RNG2[1:0] -

Table 5.15 Derivative Options

DER_OPTX[1:0]

OPERATION1 0

0 0 No derivative options used

0 1

Basic derivative. The derivative of the error from the current drive setting and the target is added

to the iterative Fan Drive Register setting (in addition to proportional and integral terms)

(default)

1 0

Step derivative. The derivative of the error from the current drive setting and the target is added to the iterative Fan Drive Register setting and is

not capped by the Fan Step Register.

1 1Both the basic derivative and the step derivative are used effectively causing the derivative term to

have double the effect of the derivative term.



Datasheet

Bit 2 - 1 - ERR_RNGx[1:0] - Control some of the advanced options that affect the error window. Whenthe measured fan speed is within the programmed error window around the target speed, then the fandrive setting is not updated. The algorithm will continue to monitor the fan speed and calculatenecessary drive setting changes based on the error; however, these changes are ignored.

5.11 Gain Registers

The Gain registers store the gain terms used by the proportional and integral portions of each of theRPM-based Fan Speed Control Algorithms. These gain terms are used as the KD, KI, and KP gainterms in a classic PID control solution.

Bits 5 - 4 - GAINDX[1:0] - Controls the derivative gain term used by the FSC algorithm as shown inTable 5.18.

Bits 3-2 - GAINIX[1:0] - Controls the integral gain term used by the FSC algorithm as shown inTable 5.18.

Bits 1-0 - GAINP[1:0] - Controls the proportional gain term used by the FSC algorithm as shown inTable 5.18.

Table 5.16 Error Range Options

ERR_RNGX[1:0]

OPERATION1 0

0 0 0 RPM (default)

0 1 50 RPM

1 0 100 RPM

1 1 200 RPM

Table 5.17 Gain Registers


35h R/W Gain 1 Register - - GAIND1[1:0] GAINI1[1:0] GAINP1[1:0] 2Ah

45h R/W Gain 2 Register - - GAIND2[1:0] GAINI2[1:0] GAINP2[1:0] 2Ah

Table 5.18 Gain Decode

GAIND OR GAINP OR GAINI [1:0]

RESPECTIVE GAIN FACTOR1 0

0 0 1x

0 1 2x

1 0 4x (default)



Datasheet

AD LT

36

46

5.12 Fan Spin Up Configuration Registers

The Fan Spin Up Configuration registers control the settings of Spin Up Routine. The Fan Spin UpConfiguration registers are software locked.

Bit 7 - 6 - DRIVE_FAIL_CNTx[1:0] - Determines how many update cycles are used for the Drive Faildetection function as shown in Table 5.20. This circuitry determines whether the fan can be driven tothe desired tach target.

Bit 5 - NOKICKx - Determines if the Spin Up Routine will drive the fan to 100% duty cycle for 1/4 ofthe programmed spin up time before driving it at the programmed level.

‘0’ (default) - The Spin Up Routine will drive the fan driver to 100% for 1/4 of the programmed spin up time before reverting to the programmed spin level.

‘1’ - The Spin Up Routine will not drive the fan driver to 100%. It will set the drive at the programmed spin level for the entire duration of the programmed spin up time.

Bits 4 - 2 - SPIN_LVLx[2:0] - Determines the final drive level that is used by the Spin Up Routine asshown in Table 5.21.

1 1 8x

Table 5.19 Fan Spin Up Configuration Registers

DR R/W REGISTER B7 B6 B5 B4 B3 B2 B1 B0 DEFAU

h R/W Fan 1 Spin Up Configuration

DRIVE_FAIL_CNT1 [1:0] NOKICK1 SPIN_LVL1[2:0] SPINUP_TIME

1 [1:0] 19h

h R/W Fan 2 Spin up Configuration

DRIVE_FAIL_CNT2 [1:0] NOKICK2 SPIN_LVL2[2:0] SPINUP_TIME

2 [1:0] 19h

Table 5.20 DRIVE_FAIL_CNT[1:0] Bit Decode

DRIVE_FAIL_CNTX[1:0]

NUMBER OF UPDATE PERIODS1 0

0 0 Disabled - the Drive Fail detection circuitry is disabled (default)

0 1 16 - the Drive Fail detection circuitry will count for 16 update periods



Table 5.18 Gain Decode (continued)

GAIND OR GAINP OR GAINI [1:0]

RESPECTIVE GAIN FACTOR1 0



Datasheet

Bit 1 -0 - SPINUP_TIMEx[1:0] - determines the maximum Spin Time that the Spin Up Routine will runfor (see Section 4.6). If a valid tachometer measurement is not detected before the Spin Time haselapsed, an interrupt will be generated. When the RPM-based Fan Speed Control Algorithm is active,the fan driver will attempt to re-start the fan immediately after the end of the last spin up attempt.

The Spin Time is set as shown in Table 5.22.

5.13 Fan Max Step Registers

Table 5.21 Spin Level

SPIN_LVLX[2:0]

SPIN UP DRIVE LEVEL2 1 0

0 0 0 30%

0 0 1 35%

0 1 0 40%

0 1 1 45%

1 0 0 50%

1 0 1 55%

1 1 0 60% (default)

1 1 1 65%

Table 5.22 Spin Time

SPINUP_TIMEX[1:0]

TOTAL SPIN UP TIME1 0

0 0 250 ms

0 1 500 ms (default)

1 0 1 sec

1 1 2 sec

Table 5.23 Fan Max Step Registers


37h R/W Fan 1 Max Step - - 32 16 8 4 2 1 10h

47h R/W Fan 2 Max Step - - 32 16 8 4 2 1 10h



Datasheet

AD T

3

4

The Fan Max Step registers, along with the Update Time, control the ramp rate of the fan driverresponse calculated by the RPM-based Fan Speed Control Algorithm. The value of the registerrepresents the maximum step size each fan driver will take between update times (see Section 5.9).

When the FSC algorithm is enabled, Ramp Rate control is automatically used. When the FSC is notactive, then Ramp Rate control can be enabled by asserting the EN_RRC bit (see Section 5.10).

APPLICATION NOTE: The UPDATE bits and Fan Step Register settings operate independently of the RPM-basedFan Speed Control Algorithm and will always limit the fan drive setting. That is, if theprogrammed fan drive setting (either as determined by the RPM-based Fan Speed ControlAlgorithm or by manual settings) exceeds the current fan drive setting by greater than theFan Step Register setting, the EMC2302 will limit the fan drive change to the value of theFan Step Register. It will use the Update Time to determine how often to update the drivesettings.

APPLICATION NOTE: If the Fan Speed Control Algorithm is used, the default settings in the Fan Configuration 2Register will cause the maximum fan step settings to be ignored.

The Fan Max Step registers are software locked.

5.14 Fan Minimum Drive Registers

The Fan Minimum Drive registers store the minimum drive setting for each RPM-based Fan SpeedControl Algorithm. The RPM-based Fan Speed Control Algorithm will not drive the fan at a level lowerthan the minimum drive unless the target Fan Speed is set at FFh (see Section 5.17).

During normal operation, if the fan stops for any reason (including low drive), the RPM-based FanSpeed Control Algorithm will attempt to restart the fan. Setting the Fan Minimum Drive Register to asetting that will maintain fan operation is a useful way to avoid potential fan oscillations as the controlcircuitry attempts to drive it at a level that cannot support fan operation.

The Fan Minimum Drive Registers are software locked.

5.15 Valid TACH Count Registers

Table 5.24 Minimum Fan Drive Registers

DR R/W REGISTER B7 B6 B5 B4 B3 B2 B1 B0 DEFAUL

8h R/WFan 1

Minimum Drive

128 64 32 16 8 4 2 1 66h(40%)

8h R/WFan 2

Minimum Drive

128 64 32 16 8 4 2 1 66h(40%)

Table 5.25 Valid TACH Count Registers


39h R/W Valid TACH Count 1 4096 2048 1024 512 256 128 64 32 F5h

49h R/W Valid TACH Count 2 4096 2048 1024 512 256 128 64 32 F5h



Datasheet

The Valid TACH Count registers store the maximum TACH Reading Register value to indicate thateach fan is spinning properly. The value is referenced at the end of the Spin Up Routine to determineif the fan has started operating and decide if the device needs to retry. See Equation [2] in Section 5.18for translating the count to an RPM.

If the TACH Reading Register value exceeds the Valid TACH Count Register (indicating that the FanRPM is below the threshold set by this count), then a stalled fan is detected. In this condition, thealgorithm will automatically begin its Spin Up Routine.

If a TACH Target setting is set above the Valid TACH Count setting, then that setting will be ignoredand the algorithm will use the current fan drive setting.

The Valid TACH Count registers are software locked.

5.16 Fan Drive Fail Band Registers

The Fan Drive Fail Band Registers store the number of tach counts used by the Fan Drive Faildetection circuitry. This circuitry is activated when the fan drive setting high byte is at FFh. When it isenabled, the actual measured fan speed is compared against the target fan speed. These registersare only used when the FSC is active.

This circuitry is used to indicate that the target fan speed at full drive is higher than the fan is actuallycapable of reaching. If the measured fan speed does not exceed the target fan speed minus the FanDrive Fail Band Register settings for a period of time longer than set by the DRIVE_FAIL_CNTx[1:0]bits, then the DRIVE_FAIL status bit will be set and an interrupt generated.

5.17 TACH Target Registers

Table 5.26 Fan Drive Fail Band Registers


3Ah R/W Fan 1 Drive

Fail Band Low Byte

16 8 4 2 1 - - - 00h

3Bh R/WFan 1 Drive Fail Band High Byte

4096 2048 1024 512 256 128 64 32 00h

4Ah R/W Fan 2 Drive

Fail Band Low Byte

16 8 4 2 1 - - - 00h

4Bh R/WFan 2 Drive Fall Band High Byte

4096 2048 1024 512 256 128 64 32 00h

Table 5.27 TACH Target Registers


3Ch R/W TACH Target 1 Low Byte 16 8 4 2 1 - - - F8h

3Dh R/W TACH Target 1 High Byte 4096 2048 1024 512 256 128 64 32 FFh



Datasheet

The TACH Target Registers hold the target tachometer value that is maintained by the RPM-basedFan Speed Control Algorithm.

The value in the TACH Target Registers will always reflect the current TACH Target value.

If one of the algorithms is enabled, setting the TACH Target Register to FFh will disable the fan driver(set the fan drive setting to 0%). Setting the TACH Target to any other value (from a setting of FFh)will cause the algorithm to invoke the Spin Up Routine after which it will function normally.

The Tach Target is not applied until the high byte is written. Once the high byte is written, the currentvalue of both high and low bytes will be used as the next Tach target.

5.18 TACH Reading Registers

The TACH Reading Registers’ contents describe the current tachometer reading for each of the fans.By default, the data represents the fan speed as the number of 32kHz clock periods that occur for asingle revolution of the fan.

Equation [2] shows the detailed conversion from TACH measurement (COUNT) to RPM while Equation[3] shows the simplified translation of TACH Reading Register count to RPM assuming a 2-pole fan,measuring 5 edges, with a frequency of 32.768kHz. These equations are solved and tabulated for easeof use in AN17.4 RPM to TACH Counts Conversion.

Whenever the high byte register is read, the corresponding low byte data will be loaded to internalshadow registers so that when the low byte is read, the data will always coincide with the previouslyread high byte.

4Ch R TACH Target 2 Low Byte 16 8 4 2 1 - - - F8h

4Dh R/W TACH Target 2 High Byte 4096 2048 1024 512 256 128 64 32 FFh

Table 5.28 TACH Reading Registers


3Eh R Fan 1 TACH 4096 2048 1024 512 256 128 64 32 FFh

3Fh R Fan 1 TACH Low Byte 16 8 4 2 1 - - - F8h

4Eh R Fan 2 TACH 4096 2048 1024 512 256 128 64 32 FFh

4Fh R Fan 2 TACH Low Byte 16 8 4 2 1 - - - F8h

Table 5.27 TACH Target Registers (continued)




Datasheet

ADD LT

EF

ADDR ULT

FDh h

5.19 Software Lock Register

The Software Lock Register controls the software locking of critical registers. This register is softwarelocked.

Bit 0 - LOCK - this bit acts on all registers that are designated SWL. When this bit is set, the lockedregisters become read only and cannot be updated.

‘0’ (default) - all SWL registers can be updated normally.

‘1’ - all SWL registers cannot be updated and a hard-reset is required to unlock them.

5.20 Product ID Register

The Product ID Register contains a unique 8-bit word that identifies the product.

where:

[2]

poles = number of poles of the fan (typically 2)

fTACH = the tachometer measurement frequency (typically

32.768kHz)

n = number of edges measured (typically 5 for a 2 pole fan)

m = the multiplier defined by the RANGE bits

[3]COUNT = TACH Reading Register

value (in decimal)

Table 5.29 Software Lock Register

R R/W REGISTER B7 B6 B5 B4 B3 B2 B1 B0 DEFAU

h R/W Software Lock - - - - - - - LOCK 00h

Table 5.30 Product ID Register

R/W REGISTER B7 B6 B5 B4 B3 B2 B1 B0 DEFA

R Product ID 0 0 1 1 0 1 1 0 36

RPM 1poles( )

-------------------- n 1–( )

COUNT 1m-----×

---------------------------------- fTACH 60×××=

RPM 3,932,160 m×COUNT

--------------------------------------=



Datasheet

A

5.21 Manufacturer ID Register

The Manufacturer ID Register contains an 8-bit word that identifies SMSC.

5.22 Revision Register

The Revision Register contains an 8-bit word that identifies the die revision.

Table 5.31 Manufacturer ID Register

DDR R/W REGISTER B7 B6 B5 B4 B3 B2 B1 B0 DEFAULT

FEh R Manufacturer ID 0 1 0 1 1 1 0 1 5Dh

Table 5.32 Revision Register


FFh R Revision 1 0 0 0 0 0 0 0 80h



Datasheet

Chapter 6 Typical Operating Curves

The following Typical Operating Curves are included.

Supply Current vs. Temperature

Supply Current vs. Supply Voltage

Fan TACH Accuracy vs. Temperature

Fan TACH Accuracy vs. Supply Voltage

PWM output frequency vs. Supply Voltage

PWM output frequency vs. Temperature

FSC Operation

Supply Current vs. Ambient Temperature

250

300

350

400

450

500

-50 0 50 100 150

Temperature (C)

Supp

ly C

urre

nt (u

A)

Supp

ly C

urre

nt (u

A)

Ambient Temperature (°C)

Supply Current vs. Supply Voltage

250

300

350

400

450

500

2.95 3.05 3.15 3.25 3.35 3.45 3.55 3.65

Supply Voltage (V)

Supp

ly C

urre

nt (u

A)

Sup

ply

Cur

rent

(uA)

Supply Voltage (V)

Tachometer Measurement Accuracy vs. Ambient Temperature

-1

-0.8

-0.6

-0.4

-0.2

0

0.2

0.4

0.6

0.8

1

-50 0 50 100 150

Temperautre (C)

Tach

Mea

sure

men

t Acc

urac

y (%

Ambient Temperature (°C)

Tach

Mea

sure

men

t Acc

urac

y (%

)

Tachometer Measurement Accuracy vs. Supply Voltage

-1

-0.8

-0.6

-0.4

-0.2

0

0.2

0.4

0.6

0.8

1

2.95 3.05 3.15 3.25 3.35 3.45 3.55 3.65

Supply Voltage (V)

Tach

Mea

sure

men

t Acc

urac

y (%

Tach

Mea

sure

men

t Acc

urac

y (%

)



Datasheet

PWM Frequency vs. Ambient TemperatureVDD = 3.3V, Base Frequncy = 26Khz

25000

25200

25400

25600

25800

26000

26200

26400

26600

26800

27000

-50 0 50 100 150Temperat ure ( C )Ambient Temperature (°C)

PW

M F

requ

ency

(Hz)

PWM Frequency vs. Supply VoltageTA = 25C, Base Frequncy = 26Khz

25000

25200

25400

25600

25800

26000

26200

26400

26600

26800

27000

2.95 3.05 3.15 3.25 3.35 3.45 3.55 3.65

Supply Voltage (V)

PW

M F

requ

ency

(Hz)

PWM Output

10x Zoom on

PWM Output

Spin Time = 1.0s; Spin Level = 55%; Updated Time = 200ms; RPM Target from 0 RPM -> 8000 RPM @ time t = 0

FSC Algorithm Spin Up Routine

t = 0 Duty Cycle Measured = 53.8%

PWM Output

10x Zoom on

PWM Output

Spin Time = 1.0s; Spin Level = 50%; UpdateTime = 200ms; RPM Target from 0 RPM -> 8000 RPM @ time t = 0

FSC Algorithm Spin Up Routine – NoKick

t = 0 Duty Cycle Measured = 50%

PWM Output

10x Zoom on

PWM Output

Update Time = 200ms; Max Step = 16 PWM counts RPM Target from 0 RPM -> 8000 RPM @ time t = 0

FSC Algorithm PWM Ramping

Spin Up Routine Ends – begins normal operation

Update Time ends, PWM duty cycle changed

Update Time ends, PWM duty cycle changed

Duty Cycle Measured



Datasheet

Chapter 7 Package Drawing

7.1 EMC2302 Package Information

Figure 7.1 EMC2302 Package Drawing - 10-Pin MSOP

AA2

A1SEATING PLANE

SIDE VIEW

ccc C

GAUGE PLANE

H

3-D VIEW

TOP VIEW

C

3

2

END VIEW

4

3 5

DETAIL "A"

NOTES:1. ALL DIMENSIONS ARE IN MILLIMETER.2. TOLERANCE ON THE TRUE POSITION OF EACH LEAD IS ± 0.04 mm AT MAXIMUM MATERIAL CONDITION.3. PACKAGE BODY DIMENSIONS "D" AND "E1" DO NOT INCLUDE MOLD/INTERLEAD PROTRUSIONS OR FLASH. MAXIMUM MOLD PROTRUSIONS OR FLASH IS 0.15 mm (0.006 INCHES) PER END AND SIDE. DIMENSIONS "D" AND "E1" ARE DETERMINED AT THE OUTERMOST EXTREMES OF THE PLASTIC BODY, INCLUDING ANY MISMATCH BETWEEN TOP AND BOTTOM PLASTIC BODY. THEY ARE DETERMINED AT DATUM PLANE "H".4. DIMENSIONS "b" AND "c" APPLY TO THE FLAT SECTION OF THE LEAD BETWEEN 0.08 mm AND 0.15 mm FROM THE LEAD TIP.5. DETAILS OF THE PIN 1 IDENTIFIER ARE OPTIONAL, BUT MUST BE LOCATED WITHIN THE ZONE INDICATED.

A INITIAL RELEASE 3/29/05 S. K.ILIEV

c

SEE DETAIL "A"

eD

E1 E

PIN 1 IDENTIFIER AREA (D/2 X E1/2)

10X b

L

(0.95)

0.25

0° - 8°

DI M AND T OL PER ASME Y14.5M - 1994

F IN ISH

M A TERIAL

DECIM ALX.XX.XXX.XXX

80 ARKAY DRIVEHAUPPAUGE, NY 11788USAANGULAR

PRINT WIT H "SCALE TO FIT" DO NOT SCALE DRAWING

CH ECKED

APPR OVED

N AM E

DRAWN

DWG NUM BER

SC ALE

TITLE

DAT E

STD C OM PLIANC E

UNLESS OTHERWISE SPECIFIEDDIM ENSI ONS ARE IN MILLIMETERS AND TOLERANCES ARE:

THIR D ANG LE PRO J ECTION

REV

S HEET

REVISION DESCRIPTION

REVISIO N HISTORY

RELEASED BYDATE

PACKAGE OUTLINE10 PIN TSSOP, 3x3 MM BODY, 0.50 MM PITCH

±1 °

-

-

±0.1±0.05±0.025

S.K.ILIEV

S.K.ILIEV

S.K.ILIEV

3/29/05

3/29/05

1:1

3/29/05

MO-10-TSSOP-3x3

JEDEC: MO-187 1 OF 1

A

C

SEATING PLANE

4



Datasheet

7.2 Package Markings

Figure 7.2 EMC2302 Package Markings

BOTTOM

LINE: 1-T – Device Number

LINE: 2-T Version, Revision, Country Code (VRCC)

ALL TOP LINES CENTER HORIZONTAL ALIGNMENT

PB-FREE/GREEN SYMBOL(Matte Sn)

2x 1.5pt

TOP

e3

PIN 1

LINE: 1-B – Date Code (YYWW)

LINE: 2-B – First 3 Digits of Lot Number

3x 1.5pt

PIN 1

LINE: 3-B – Last 4 Digits of Lot Number

2 3 0 2

V R C C

Y Y W W

1 2 3

4 5 6 a



Datasheet


Chapter 8 Datasheet Revision History

Table 8.1 Customer Revision History

REVISION LEVEL & DATE SECTION/FIGURE/ENTRY CORRECTION

Rev. 1.3 (05-18-11) Section 4.8, "Watchdog Timer"

The ALERT# pin is asserted when the watchdog is triggered.

Section 5.2, "Configuration Register"

Corrected description for MASK bit. Changed “If any bit in either status register is set, the ALERT# pins will be asserted (unless individually masked via the Mask Register)” to “If any bit in the status registers is set, the ALERT# pin will be asserted (unless individually masked via the Fan Interrupt Enable Register)”.

Rev. 1.2 (03-22-10) Table 2.3, "SMBus Electrical Specifications"

Updated SMBus Data Hold Time spec to 0 us

Rev. 1.1 (10-12-09) Table 2.2, "Electrical Specifications"

Tachometer Setting Accuracy max was changed from +/-3% to +/-2%.

Chapter 6, Typical Operating Curves

Added typical operating curves

Ordering Information Added EMC2302-2 for 2nd SMBus address

Rev. 1.0 (05-15-09) Initial release of datasheet

Documents

EMC2302 - Dual RPM-Based PWM Fan Controller Datasheet - SMSC