Issue 3, December 2006

IntroductionStephen CaldwellDirector, Home Appliance Solutions Group

Welcome to the third issue of the 3V Newsletter created by theApplication Engineering community at Microchip Technology.This exciting series of newsletters is designed to cover thetechnical and logistical challenges of migrating from 5V to 3V.In previous editions, we discussed the business need formoving to 3V only products. We touched upon some of thetechnical advantages that 3V can provide. We provided hintson creating basic 3V power supplies and hints on how tointerface 3V and 5V products. Historically, Microchip has released microcontrollers thatoperated from 2V to 5V. To take advantage of advancedtechnologies, we introduced several product families that runfrom 2V to 3.6V. Check out Microchip’s newest 16-bit productfamilies – www.microchip.com/16bit. In the future, Microchipwill continue to introduce both 5V and 3V new products.

This issue covers a broad range of subjects including anarticle that introduces Microchip’s next generation high-speedemulator for PIC® Microcontrollers. Other articles coverrobustness, interface solution and standby current.Future 3V newsletters will cover topics such as powersupplies, noise, sensors, communications, and drivers. Thisseries of newsletters will also inform the reader of availableapplication notes, migration documents and web resourcesapplicable of this topic. For the latest information, make sureto visit www.microchip.com/3volts. If you have comments or suggestions for an article, pleasesend an e-mail to 3V@microchip.comEnjoy!

Need Help?We can help you select the device and tool that is right for you, andhelp you with a number of different technical challenges. Submit aticket to support.microchip.com to get your questions answered.

© 2006 Microchip Technology Inc. 1

In This IssueRobustness of 3V Systems .............................................. 2Using MPLAB® REAL ICE™ Probe In Low-VoltageApplications......................................................................3PICDEM™ HPC Explorer Board ...................................... 4dsPICDEM™ 1.1 Plus...................................................... 4Tip #1 Standby Current Reduction Techniquefor J Devices .................................................................... 4Bridging The Rails ............................................................ 5Tip #2 Driving Bipolar Transistors ....................................7

Recommended ReadingEMC NewsletterIn these newsletters, you will find a wealth of information including ideas and design tips you can use to improve Electromagnetic Compatibility (EMC) when using our products. To obtain copies of these newsletters, go to www.microchip.com/emc.

Tips and TricksRemember to Read the Electrical Specifications

It is very important to read the electrical specificationswhen mixing 3V and 5V devices. Specifically, you mustreview the input and output thresholds and output currentdrive capabilities. The VIL and VOL specs are usually notan issue since CMOS outputs drive very close to groundfor a low signal, no matter what the technology.

The major concern is, can a 3V output drive a 5V input andvice versa. A 3V output will typically drive within no lowerthan 2.3V (VDD-0.7V). A 5V TTL input will accept 2V as aminimum to be recognized as a logic ‘1’. A Schmitt Trigger(ST) type input will typically require 4V (VDD * 0.8) as aminimum. Therefore, 3V outputs can drive 5V TTL inputsbut not 5V ST inputs.

3V Newsletter

Robustness of 3V SystemsSteve CaldwellDirector, Home Appliance Solutions Group

System designers with experience designing 5Vsystems may have concerns when migrating to theirfirst 3V system. They will need to redesign the powersupply. They will need to source 3V equivalent prod-ucts. They may even need to tweak the gain on the opamps. Most designers are able to negotiate thechallenges and deliver a functional board with minimalimpact to the schedule. However, these designers maybe uncertain about the robustness of a 3V systemcompared to their existing 5V systems.

A system is robust if it behaves predictably andrecovers gracefully after a catastrophic event. A plan toimprove robustness should address schematics, firm-ware, PCB layout, filters, component selection, testingand disciplined engineering work. Typically there is nota one panacea to designing a robust system. EMC is a complex subject and is defined as the abilityof an electrical system to function without error in itsintended environment without disturbing anything else,including itself, in that electromagnetic environment.EMC can be categorized as emissions (EMI) orsusceptibility (ESD, EFT, Latch-up). There is good news for emissions. With equalfrequency and current, a 3V system will use less powerthan an equivalent 5V system. Thus, 3V systems willemit less conducted and radiated noise (see Figure 1).

FIGURE 1: 20 MHz CLOCK, VDD-5V AND 3V, X-AXIS

The first robustness thought of a system designer isthat as the transistor geometry shrinks, the productsare inherently less robust and more susceptible tonoise. The second thought is that there is lessguardband at 3V compared to 5V. Addressing susceptibility is not inherently easy.Whereas emissions can be measured for a component,susceptibility is typically system related. The appropri-ate question is not, “Is my component robust?”, butrather, “Is my system robust?”Designers must defend their systems against noise.They should, understand the noise source, reduce thegenerated noise, filter the noise at the source, and thenlocally protect critical components. There is a wealth ofdata at www.microchip.com/EMC on this subject.Whether a critical component is 3V or 5V, a systemdesigner should take precautions to protect this com-ponent. Of course, every component inherentlybehaves uniquely in a given system and situation. So,it behooves a designer to select a robust component.

Microchip Technology has designed the 3V PIC®Microcontroller families to help our customer meet theirdemanding robust requirements. These productsinclude watchdog timers, brown-out detects, power-uptimers, and reliable Flash memory. Additionally, thesefamilies were produced with proprietary, advanceddesign and manufacturing techniques to negate theeffects of the smaller transistors. The 3V PIC Microcon-troller families have similar or better susceptibilityresults in equivalent systems compared to oldergeneration PIC Microcontroller families. Microchip will publish a white paper on the Robustnessof the PIC18FXXJXX family in 1CQ07. This paper willinclude EMI, ESD, EFT and latch-up data as well asADC performance. Check www.microchip.com/3v fordetails. The system designer is ultimately responsible forsystem robustness. The designer should understandthe noise sources, work to reduce this noise, appropri-ately filter the remaining noise, and protect criticalcomponents from residual noise. Selecting Microchip’sPIC microcontrollers on your next design will give youa head start in designing a robust system.

Microcontroller, 20 MHz Clock, Vdd=5V, X-Axis, IEC61967-2, SAE J1752/3 Band E (400 - 600 MHz)

-10

-5

0

5

10

15

20

25

400 425 450 475 500 525 550 575 600

Frequency (MHz)

dBuV

Level 1Level 2Level 3

Microcontroller, 20 MHz Clock, Vdd=3V, X-Axis, IEC61967-2, SAE J1752/3 Band E (400 - 600 MHz)

-10

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2 © 2006 Microchip Technology Inc.

3V Newsletter

Using MPLAB® REAL ICE™ Probe In Low-Voltage ApplicationsAl RodriguezStaff Engineer, Dev. Tools HW

MPLAB REAL ICE In-Circuit Emulator System isMicrochip’s next generation high-speed emulator forMicrochip Flash DSC and MCU devices. It debugs andprograms PIC® and dsPIC® Flash microcontrollers withthe easy-to-use but powerful graphical user interface ofthe MPLAB Integrated Development Environment(IDE), included with each kit. MPLAB REAL ICE is ideal for 3V applications. MPLABREAL ICE operates over a target VDD range of 2V to5V. One of the key characteristics of MPLAB REAL ICEis that it senses the target voltage level. Once the volt-age level is known, it is used as a voltage reference toits own internal power supply and powers up the clockand data signal drivers. Additionally, the current consumption from the target isless than 1 ma and is ideal for battery-powered appli-cations where the current drain by an external systemcan not be tolerated.Not requiring an external supply is another significantcharacteristic of MPLAB REAL ICE. All power isderived from the USB port, eliminating power supplysequencing issues in a multiple voltage system.This approach makes automatic target detect possibleand the behavior is more like a plug and play featurewhen connected to the target application.During power-up, as the MPLAB REAL ICE is initializ-ing, it conducts a self-test and diagnostics sequenceand is able to detect the target and a device attached.The MPLAB REAL ICE also contains a 14-pin headerthat includes eight logic probes. These logic probeinput and output connections can be used as 8-inde-pendent outputs that can be used for triggering externalequipment or conversely can be used to halt theMPLAB REAL ICE system from an external source withselectable logic transition or level. The I/O levels alsomatch the application voltage levels.The MPLAB REAL ICE comes with two-interfaceconfiguration. The standard RJ11 6-pin jack connectorinterface can be used with many Microchip Technologydemo boards, which follow the traditional ICSP™interface. The high-speed interface uses two RJ45jacks and includes LVDS level translators. This config-uration comes standard with a CAT5 3-foot cable andcan easily be extended to other lengths, which is handywhen the target device and development computersystem are not in close proximity.

MPLAB REAL ICE offers focused debugging facilitiesfor finding hard bugs. Among them are data capture forstreaming data valuation, Trace for code execution,and Log for synchronized variable valuation. Addition-ally, the register file and special function registers canbe evaluated without a significant speed penalty whileperforming debug operations such as single steps.

FIGURE 1: MPLAB® REAL ICE™ EMULATION

MPLAB REAL ICE offers the following advantages:- Low cost - Full speed emulation- Fast debugging and programming- High speed USB 2.0 communication protocol- Trace analysis- Ruggedized probe interface- Legacy And high speed connectivity- Long interconnection cables

MPLAB REAL ICE features:- Real-time execution- Fast programming- USB 2.0 high speed interface to PC

(480 Mb/s) - MPLAB IDE integration (included free) - Over voltage/short-circuit monitor protection- Low voltage: to 2.0 volts (2.0 to 6.0 range) - Read/Write program and data memory of

microcontroller- Erase of program memory space with verifi-

cation- Stopwatch- Real time watch- Capture trace to log instruction execution and

variable contents (~10KB/s at 4MHz 16-bit core)

- Port trace for high speed upload of trace data- High Speed Option allows full speed emula-

tion, high speed trace upload and long (vali-dated to 3 meters) cables

- Processor Paks provide debug interface with no reserved pins

© 2006 Microchip Technology Inc. 3

3V Newsletter

4 © 2006 Microchip Technology Inc.

PICDEM™ HPC Explorer BoardThis low-cost demo board is the ideal tool to evaluatethe performance of Microchip high-end 8-bit microcon-trollers of the PIC18F J-series 3V devices.The board features a PIC18F8722 microcontroller,which is the superset of the entire 64- and 80-pinPIC18FXXXX general purpose 5V MCU family.The J-series products have Plug-in Modules that willautomatically configure the voltage of the HPCExplorer Board to be 3V.Plug-in Modules to HPC Explorer Board for PIC18J-series devices:• Part Number: MA180011 – PIC18F25J10 Plug-in

Module (also used to evaluate PIC18F24J10) • Part Number: MA180012 – PIC18LF25J10 Plug-in

Module (also used to evaluate PIC18LF24J10) • Part Number: MA180013 – PIC18F45J10 Plug-in

Module (also used to evaluate PIC18F44J10) • Part Number: MA180014 – PIC18LF45J10 Plug-in

Module (also used to evaluate PIC18LF44J10) • Part Number: MA180015 - PIC18F87J10 Plug-in

Module (also used to evaluate PIC18F86J1X, PIC18F85J1X, PIC18F67J10, PIC18F66J1X, PIC18F65J1X)

FIGURE 1: PICDEM™ HPC EXPLORER BOARD

dsPICDEM™ 1.1 PlusThe dsPICDEM 1.1 Plus Development Board kit servesas a development and evaluation tool for dsPIC30F/33F High Performance Digital Signal Controllers andPIC24H/PIC24F PIC microcontrollers.The board features an active demonstration programloaded on the installed device. Several programfunctions are selectable via a menu system displayedon the LCD. These include: temperature and voltagemeasurements, frequency domain characteristics of asinewave signal generated on-board from a digitalpotentiometer, FIR and IIR digital filter selections andDTMF tone generation using the Codec interfaceperipheral (external speaker required).

FIGURE 2: dsPICDEM™ 1.1 PLUS DEV. BOARD

TIP #1 Standby Current Reduction Technique for J-Series DevicesThe standby current (base IPD) is an important param-eter for some applications. This article describes a sim-ple design tip to reduce IPD on PIC® J-series devices.They use an internal voltage regulator to power coreand peripheral logic.Disabling it could save approximately 20 μA in standbycurrent on initial PIC18 J-series devices and around 3 μA in the newer one.In this case, 2.7V or less must be supplied to VDDCOREpin. One option is to use the solution described below.

FIGURE 1: DIODE AS A VOLTAGE REGULATOR

VDD

VDDCORE

VssENVREG+BuckBoost Conv

PICXXJXXXX

Constant 3V

A diode is used as a cheap voltage regulator. In thiscase due to the diode drop, the VDDcore will remainconstant around 2.4V. This circuit can be used if thevoltage source generates constant 3V. Examples of voltage source:

- A battery like button cell that has almost flat discharge curve. (i.e., the voltage stays constant at 3V throughout battery’s useful life span).

- A battery that has a wide voltage range and using a voltage regulator or buck boost converter to ensure constant voltage.

You must check VDD and VDDCORE voltage rangespecification before selecting VDD source and thediode.

3V Newsletter

Bridging The RailsGaurang KavaiyaManager, Applications Group

The 5V power supply used to be the most popular railin embedded systems. But as discussed in the previ-ous 3V newsletter, most components are movingtoward lower rails to take advantage of the industry’snewest trends. On the other hand, some componentsin the system take longer than others to transition.Therefore, in this transition phase, some componentsin the system may require different power-supply rails(i.e., a 5V device in a 3.3V system, and vice versa). Itcreates some design challenges for an embeddeddesigner.One solution is to use a 5V device with TTL inputs(Figure 1). The VIH(min) for a TTL device is 2.1V (forthe VDD of 5V). Most 3.3V devices can support a muchhigher VOH level, even at a high load rate. In this case,the solution is to swap your peripheral device with anequivalent device having TTL-compatible inputs.

FIGURE 1: USE A 5V DEVICE WITH TTL INPUTS

If you are using a standard digital-logic family that mustrun at 5V, you can find an equivalent device with TTLinputs. For example, instead of the 74HC family, youcan use the 74HCT family. If you need level translator,then use the ‘HCT’ or ‘VHCT’ type of digital buffer. Inmost situations, this TTL-input solution tends to becheaper than the use of dedicated level translators.The VOH level of the device operating at 3.3V is slightlybelow the VIH (0.7VDD = 3.5V) of the CMOS deviceoperating at 5V. One simple solution is to use a diodeto provide the required voltage shift.

FIGURE 2: CIRCUIT SHIFTS OUTPUT TO BRING IN RANGE FOR 5V INPUT

The Figure 2 circuit shifts the output by approximately0.6V on the positive side. This 0.6V shift to the CMOSoutput brings it in range for 5V CMOS input. The sameamount of shift is applied to the logic low signal. How-ever, VIL (max) for the CMOS input tends to be around1.5V, so the shifted signal does not violate the VIL spec.You need to consider a few things regarding this con-figuration. When the 3.3V device outputs a zero logiclevel, it increases the current draw. You should alsolook at the VOL spec of the 3.3V device for this currentsink. Typically, the higher the sink current, the higherthe VIL. Here, you should be careful to avoid violationof the VIL spec. If the CMOS output VOL is higher, thenyou should consider increasing the pull-up resistorvalue. If the resistor value is too high, the diode biascurrent will be low and it may not be able to switch fast.Devices like Microchip’s PIC18F J-series and thePIC24F 16-bit family offer unique features to simplifythe 5V interface. They provide the option to generate a5V output with an external 5V pull-up resistor. The 3.3Vdevice drives a 3.3V output, but it can tolerate a 5Vinput. The digitally controlled open-drain output capa-bility on these pins allows you to pull this pin to 5V, with-out violating any specs. This feature supports a simpleinterface to 5V devices with CMOS inputs (Figure 3).

FIGURE 3: A PULL-UP RESISTOR ON OPEN DRAIN OUTPUT TO GENERATE 5V OUTPUT

MCU Peripheral

+3.3V +5V

TTL InputsVih(min) = 2.1V

CMOSoutput

MCU Peripheral

+3.3V +5V

CMOS InputsVih(min) = 3.5VVil(max) = 1.5V

CMOS output

PIC24F MCU Peripheral

+3.3V +5V

CMOS InputsVih(min) = 3.5V

CMOS output

5V tolerant input

CMOS output

© 2006 Microchip Technology Inc. 5

3V Newsletter

When using a pull-up resistor configuration (Figure 3),you need to consider the capacitance of the connectionbetween the two devices to determine the rise/fall rate(as does the maximum switching frequency) of thesignal on this port pin, and the resistor value that isappropriate for the application. Consider the followingequation:

Where τ = RC time constant, R * CPVDD = VDD of he Peripheral voltagePVIH(min) = The VIH(min) value of the peripheral.

If we use the following typical values,

Pull up resistor R = 1KResultant capacitance C due to pin and PCB capacitance= 10 pF PVDD = 5VPVIH(min) = 0.7 * VDD = 3.5V

The resultant Rise/ fall time ≈ 12nSIf the minimum acceptable pulse width for this rise/falltime is 50 nS, the maximum output frequency is 20MHz, which is good enough for most peripheralinteractions.This configuration has one side effect. When the MCUdrives the logic low, the extra current is burned througha pull-up resistor. The pull-up resistor offers designtrade-offs for speed against current draw. You need toselect a compromise value that provides the requiredspeed and current consumption for the application.

Some may say that you can’t use this kind of configura-tion to drive a low-impedance load. If you want to drivea 5V relay, what should you do? Fortunately, the abovefeature is also helpful for driving low-impedance loadslike relays. (See Figure 4 for the circuit-configurationinformation.) To drive the load, define the pin as an out-put and drive it low. The only limiting factor here is thecurrent-sinking capability of the device. To turn off theload, define the pin as an input. This will turn the load offand will result in 5 Volts at input. The pin is 5V-tolerant,so this is a valid operation. In other words, you need tomaintain logic low on output latch and toggle TRIS(input/output control register) to turn the load on/off.

FIGURE 4: A CIRCUIT CONFIGURATION FOR DRIVING LOW-IMPEDANCE LOADS

You now have an effective way to bridge the 5V and3.3V rails. It’s possible to come up with similar low-cost,intelligent solutions to bridge two rails during the transi-tion phase. It is also very likely that most devices willsoon move to a lower rail, eliminating the need tobridge the rails. In the meantime, the methods in thisarticle should help you to take advantage of the newesttrends in the semiconductor industry and lower yoursystem costs.

⎟⎠⎞

⎜⎝⎛

−=

(min)ln/

IHDD

DD

PVPV

PVFalltimeRise τ

3.3V Device with5V tolerant I/P

5V

Load on MCU Pin defined as O/P

3.3V Device with 5V tolerant I/P

5V

Load Off MCU Pin defined as I/P

ELECTRICAL SPECIFICATIONS

Device VDD Supply Digital only I/O Ports Input High Voltage Maximum Current Source/Sink

PIC® and dsPIC30F 5.5V 5.5V Max 25 mAPIC18F J-series 2.0-3.6V 5.5V Max 4/8/25 mA (I/O port dependent)PIC24F 2.0-3.6V 5.5V Max 18 mAPIC24H 3.0-3.6V 5.5V Max 4 mAdsPIC33F 3.0-3.6V 5.5V Max 4 mA

6 © 2006 Microchip Technology Inc.

3V Newsletter

TIP #2 Driving Bipolar TransistorsWhen driving Bipolar transistors, the amount of basecurrent “drive” and forward current gain (Β/hFE) willdetermine how much current the transistor can sink.When driven by a microcontroller I/O port, the basedrive current is calculated using the port voltage andthe port current limit (typically 20 mA). When using3.3V technology, smaller value base current limitingresistors should be used to ensure sufficient base driveto saturate the transistor.

FIGURE 1: DRIVING BIPOLAR TRANSISTORS USING MICROCONTROLLER I/O PORT

The value of RBASE will depend on the microcontrollersupply voltage. Equation 1 describes how to calculateRBASE.

TABLE 1: BIPOLAR TRANSISTOR DC SPECIFICATIONS

Characteristic Sym Min Max Unit Test Condition

OFF CHARACTERISTICSCollector-Base Breakdown voltage

V(BR)CBO 60 — V IC = 50 μA, IE = 0

Collector- Emitter Breakdown Voltage

V(BR)CEO 50 — V IC = 1.0 mA, IB = 0

Emitter-Base Breakdown Voltage

V(BR)EBO 7.0 — V IE = 50 μA, IC = 0

Collector Cutoff Current

ICBO — 100 nA VCB = 60V

Emitter Cutoff Current

IEBO — 100 nA VEB = 7.0V

ON CHARACTERISTICSDC Current Gain hFE 120

180270

270390560

—VCE = 6.0V, IC = 1.0 mA

Collector- Emitter Saturation Voltage

VCE(SAT) — 0.4 V IC = 50 mA, IB = 5.0 mA

VBE Forward Drop

+

-RLOAD

VLOAD

hFE (Forward Gain)

+VDD RBASE

When using bipolar transistors as switches to turn onand off loads controlled by the microcontroller I/O portpin, use the minimum hFE specification and margin toensure complete device saturation.

EQUATION 1: CALCULATING THE BASE RESISTOR VALUE

3V technology example:VDD = +3V, VLOAD = +40V, RLOAD = 400Ω, hFE min. = 180, VBE = 0.7VRBASE = 4.14 kΩ, I/O port current = 556 μA5V technology example:VDD = +5V, VLOAD = +40V, RLOAD = 400Ω, hFE min. = 180, VBE = 0.7VRBASE = 7.74 kΩ, I/O port current = 556 μAFor both examples, it is good practice to increase basecurrent for margin. Driving the base with 1 mA to 2 mAwould ensure saturation at the expense of increasingthe input power consumption.

RBASE = (VDD – VBE)XhFEXRLOAD

VLOAD

© 2006 Microchip Technology Inc. 7

3V Newsletter

NOTES:

8 © 2006 Microchip Technology Inc.

Recent IssuesThe current issue of this newsletter is available from the Microchip web site at http://www.microchip.com/3Volts.

ISSUE 2, MARCH 2006• Introduction• “Different Ways to Develop 3V From 5V for Multi-Voltage Applications”• “Fundamentals on Digital Interface Using Two Rails”• “TIP #1 Lower Cost Alternative Power System Using 3 Rectifier Diodes”• “3V VDD FAQ Items”• “Utilizing CAN and LIN in 3 Volt Embedded Designs”• “TIP #2 Driving N-Channel MOSFET Transistors”

ISSUE 1, DECEMBER 2005• “Why 3V”• “Programming at 3V VDD”• “Serial EEPROMs for 3V Applications”• “Driving Microcontrollers to 3V”• “Microchip Provides an Impressive Portfolio of Low-Voltage Analog and Interface Design Solutions”

IInformation contained in this publication regarding deviceapplications and the like is provided only for your convenienceand may be superseded by updates. It is your responsibility toensure that your application meets with your specifications.MICROCHIP MAKES NO REPRESENTATIONS OR WAR-RANTIES OF ANY KIND WHETHER EXPRESS OR IMPLIED,WRITTEN OR ORAL, STATUTORY OR OTHERWISE,RELATED TO THE INFORMATION, INCLUDING BUT NOTLIMITED TO ITS CONDITION, QUALITY, PERFORMANCE,MERCHANTABILITY OR FITNESS FOR PURPOSE.Microchip disclaims all liability arising from this information andits use. Use of Microchip devices in life support and/or safetyapplications is entirely at the buyer’s risk, and the buyer agreesto defend, indemnify and hold harmless Microchip from any andall damages, claims, suits, or expenses resulting from suchuse. No licenses are conveyed, implicitly or otherwise, underany Microchip intellectual property rights.

© 2006 Microchip Technology Inc.

Trademarks

The Microchip name and logo, the Microchip logo, Accuron, dsPIC, KEELOQ, microID, MPLAB, PIC, PICmicro, PICSTART, PRO MATE, PowerSmart, rfPIC, and SmartShunt are registered trademarks of Microchip Technology Incorporated in the U.S.A. and other countries.

AmpLab, FilterLab, Migratable Memory, MXDEV, MXLAB, SEEVAL, SmartSensor and The Embedded Control Solutions Company are registered trademarks of Microchip Technology Incorporated in the U.S.A.

Analog-for-the-Digital Age, Application Maestro, CodeGuard, dsPICDEM, dsPICDEM.net, dsPICworks, ECAN, ECONOMONITOR, FanSense, FlexROM, fuzzyLAB, In-Circuit Serial Programming, ICSP, ICEPIC, Linear Active Thermistor, Mindi, MiWi, MPASM, MPLIB, MPLINK, PICkit, PICDEM, PICDEM.net, PICLAB, PICtail, PowerCal, PowerInfo, PowerMate, PowerTool, REAL ICE, rfLAB, rfPICDEM, Select Mode, Smart Serial, SmartTel, Total Endurance, UNI/O, WiperLock and ZENA are trademarks of Microchip Technology Incorporated in the U.S.A. and other countries.

SQTP is a service mark of Microchip Technology Incorporated in the U.S.A.

All other trademarks mentioned herein are property of their respective companies.

© 2006, Microchip Technology Incorporated, Printed in the U.S.A., All Rights Reserved.

Printed on recycled paper.

9

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10 © 2006 Microchip Technology Inc.

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WORLDWIDE SALES AND SERVICE

10/19/06

IntroductionIn This IssuePICDEM™ HPC Explorer BoardFIGURE 1: PICDEM™ HPC Explorer Board

dsPICDEM™ 1.1 PlusFIGURE 2: dsPICDEM™ 1.1 Plus Dev. Board

TIP #1 Standby Current Reduction Technique for J-Series DevicesFIGURE 1: Diode as a Voltage Regulator

Robustness of 3V SystemsFIGURE 1: 20 MHz Clock, Vdd-5V and 3V, X-axis

Using MPLAB® REAL ICE™ Probe In Low-Voltage ApplicationsFIGURE 1: MPLAB® REAL ICE™ EMULATION

Bridging The RailsFIGURE 1: Use a 5V Device With TTL InputsFIGURE 2: Circuit Shifts Output to Bring in Range for 5V InputFIGURE 3: A Pull-Up Resistor on Open Drain Output to Generate 5V OutputFIGURE 4: A Circuit Configuration for Driving Low- Impedance Loads

TIP #2 Driving Bipolar TransistorsFIGURE 1: Driving Bipolar Transistors Using Microcontroller I/O PortTABLE 1: Bipolar Transistor DC Specifications

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