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Application Note

AN000363

CCS801

Design Guidelines

v3-00 • 2018-May-10

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Application Note • PUBLIC AN000363 • v3-00 • 2018-May-10 27 │ 2

Content Guide

1 Introduction .................................... 3

2 Operating Modes ........................... 4

3 Heater Control ................................ 5

3.1 Calibration .................................................... 5 3.2 Heater Measurements and Control .............. 6 3.3 PI Control ..................................................... 7

4 Sensor Measurement Control ....... 9

5 Hardware Design Considerations ............................ 10

5.1 EE Block Diagram ...................................... 10 5.2 Selection of Components ........................... 12 5.3 Development Board Details ....................... 16

6 Mechanic and Thermal Considerations ............................ 20

6.1 Sensor Placement and Ambient Exchange 20 6.2 Relative Humidity and Temperature

Compensation ............................................ 20 6.3 Thermal Considerations ............................. 20 6.4 Implementation Examples (for illustration

purpose only) ............................................. 22

7 Product Assembly and Materials 23

8 Summary ...................................... 24

9 References ................................... 25

10 Revision Information ................... 26

11 Legal Information ........................ 27

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Document Feedback CCS801 Introduction


1 Introduction

This application note describes the design guidelines in terms of CCS801 operating modes, heater

control, sensor measurement control, hardware design considerations, mechanical and thermal

considerations and product assembly requirements for CCS801.

CCS801 is an ultra-low power MOX gas sensor which will detect a wide range of Volatile Organic

Compounds (VOCs) such as Ethanol and can be used for applications which support indoor air quality

monitoring. CCS801 with software algorithms can be used as an equivalent carbon dioxide (eCO2)

sensor to represent eCO2 levels in real world environments, where the main source of VOCs is from

humans.

The typical configuration for CCS801 which is an analogue MOX gas sensor is shown in Figure 1.

Figure 1 :

CCS801 Sensor Configuration

For CCS801 a supply voltage (VH) is provided to the integrated micro-heater (RH) to heat up the heater

to target temperature and the gas concentration can be correlated to the change in resistance of the

MOX sensing layer (RS).

Heater driver control software regulates supply voltage to RH with help of heater drive circuit to

maintain stable target heater temperature with ambient temperature variations. It works on a principal

that heater resistance changes with temperature. Due to manufacturing reasons, heater resistance for

the target temperature is unique to a sensor. A calibration step need to be performed to map target

temperature to resistance of heater. The heater can be operated in constant mode or pulsed mode to

reduce power consumption. The sensitive layer acquisition control software measure the sensitive

layer resistance (RS) at appropriate with help of sensitive layer acquisition circuit.

CCS801

RH RS

micro controller

sensitive layer .acquisition

control

heater driver

control MOX library

heater driver circuit

sensitive layer

acquisition circuit


Document Feedback CCS801 Operating Modes


2 Operating Modes

CCS801 can be operated in constant power mode known as 1s mode or operated in pulsed mode

(making occasional measurements and turning the heater off when not needed) to reduce overall

power consumption. Figure 2 below shows the different operating modes supported in the MOX

software libraries for CCS801. Refer to ENS MOX Library API reference guide for more details.

Figure 2:

Diagram of the Different Operating Modes

In constant power mode the heater is constantly heated up to 330°C. The MOX resistance should be

read with an ADC at the end of measurement phase and the result written into the MOX software

library.

In pulse modes the heater is first heated to 390°C for 0.5s and then the heater drive needs to be

changed to heat up heater to 330°C for 1s. At close to the end of this pulse the MOX resistance

should be read with an ADC and the result written into the MOX software library.

Please see section 3 for details on different heater drive options.

For pulse mode operation the pulses must be controllable to 1ms time intervals and the ADC sample

points should also be controllable to 10ms. The timing is less important in 1sec mode.

time

acquistion

1000ms 58500ms

60s

time

acquisition

He

ater

Te

mpe

ratu

re

0

time

acquistion

1000ms 8500ms

Conditioning phase

Measurement phase

Cold phase(Power saving)

10s

10s pulse mode

60s pulse mode

DC mode

0

0

Conditioning phase

Measurement phase

1000ms 1000ms 1000ms 1000ms 1000ms

330°C

Hea

ter

Tem

pera

ture 330°C

390°C

He

ater

Te

mpe

ratu

re 390°C330°C

Cold phase(Power saving)


Document Feedback CCS801 Heater Control


3 Heater Control

The application needs to follow specific steps (calibration procedure) to find out target heater

resistance for each sensor that maps to target temperature. This is one-time procedure.

3.1 Calibration

Measure heater resistance (R0) at known temperature (T0). This measurement is typically done at the

room temperature. The measured resistance R0 is called as cold resistance (refer to section 3.1.1).

The target heater resistance(R) for a given target temperature (T) is calculated using below formula.

R = (R0 − CR0 + DR0) × [1 + α(T − T0) + β(T − T0)2] + CR0 − DR0

R is target heater resistance at target temperature T

R0 is resistance of heater at known temperature T0

α = 2.05 x 10-3/K β = 0.3 x 10-6/K2

C = 0.24 D = 0.063

Target heater resistance (R) is called set point. Since pulse modes have conditioning and

measurement phases, two set points need to be calculated. Target temperature for conditioning and

measurement phases are 390°C and 330°C respectively.

3.1.1 Cold Resistance Measurement

Measurement of cold resistance is an important step in calibration procedure.

Figure 4 shows application circuit for CCS801. The DAC, resistor R1 and heater (RH) forms voltage

divider circuit. The micro-heater (RH) will be heated up very quickly with supply voltage. So the cold

measurement should be done very quickly.

Apply specific voltage (Vdac = 2.8V) through DAC for short time (~20µs) and measure voltage (Vadc)

across RH using ADC. Note that ADC measurement must be completed within ~20µs after setting

DAC. Now, cold resistance can be calculated using voltage divider formula.

R0 = R1 * Vadc/ (Vdac – Vadc)

It is recommended to take multiple (e.g. 4) resistance measurements and compute mean of all reading

to get final cold resistance. The accuracy of cold resistance can be verified by measuring RH of

standalone sensor (disconnecting other components from circuit) using multi-meter at same known

temperature. The final cold resistance measured using calibration procedure should be within ±0.5Ω of

resistance value measured using multi-meter.




3.2 Heater Measurements and Control

It is recommended to measure and control heater periodically (every 10ms) to maintain stable heater

temperature due to ambient temperature variations. In each operating mode (Figure 2), operation is

broken down into 10ms blocks. Heater resistance (RH) is measured and controlled at the end of each

10ms block.

Figure 3:

Heater Measurements and Control Timing

The heater driver control software on the MCU calculates the current heater resistance (refer to

section 3.1.1) periodically by measuring voltage across heater (RH) in conditioning/measurement

phases. Then it compares calculated RH with set point resistance and adjusts DAC output accordingly

to maintain stable heater resistance. This control can be done in application software by implementing

control loop. The control loop can be implemented either by using custom control or standard

Proportional-Integral (PI) control methods.

330°C

Conditioning phase1.6V equivalent

500 ms50 x 10 ms blocks

Off

Measurement phase1.4V equivalent

1000 ms100 x 10 ms blocks

Cold phase 8500 ms (10S mode)58500 ms (60S mode)

………..

……………..

110ms

210ms

310ms

5010ms

110ms

10010ms

9910ms

9810ms

210ms ……………..

9710ms

9610ms

9510ms

……………………………………………………. Heater controlled at the end of each 10 msec block ………………………………………………...Heater OFF

MOXON

ADCs R1

ADCs R2

ADCs R3

ADCs R4

MOX OFF MOX OFF

390°C




3.3 PI Control

Refer to https://en.wikipedia.org/wiki/PID_controller for more information on PI loop working principles.

Here are typical steps to control heater.

1. Start DAC with some reasonable value

2. Measure current heater resistance (RH) after 10ms

3. Calculate error (e) by subtracting current RH from set point

4. Calculate the DAC value to be set by using PI control loop formula

d = Kp * e + Ki * i

Kp Proportional gain

Ki Integral gain

e Error in heater resistance (calculated in step2).

i Integral error accumulator (sum of the errors over time)

d DAC value to be set

5. Set the DAC with value obtained in step-4

6. Go to step-2 if current phase (conditioning/measurement) is in progress

Kp and Ki are proportional and integral gain constants and their values are calculated by following

below tuning procedure.

PI loop tuning steps:

Step1:

● Set Ki to 0

● Choose Kp so big that heater resistance oscillates.

In one second time, heater is controlled 100 times (heater controlled every 10ms). Set Kp to some

initial value (e.g. 1) and run the control loop for one second. Store all 100 measured heater resistance

values in a global buffer and analyze them (whether oscillations increasing or dying) at the end of one

second time. Now, adjust Kp (e.g. multiply or divide by 2) value and repeat earlier procedure until

heater resistance values start oscillating.

● Decrease (e.g. divide by 2) Kp, run control loop for one second and analyze heater resistance

values. Repeat this procedure until there are no oscillations.

● This finds the critical value for Kp (border between oscillation dying out and going into

oscillation)

● Divide critical value by 4 (can go up to 10) and set as Kp

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Step2:

● Set Kp to critical value obtained in Step-1

● Choose Ki so big that heater resistance oscillates. Follow same procedure as above.

● Decrease (e.g. divide by 2) Ki, run control loop for one second and analyze heater resistance

values. Repeat this procedure until there are no oscillations.

● This finds the critical value for Ki (border between oscillation dying out and going into oscillation)

● Divide critical value by 4 (can go up to 10) and set as Ki

Step3:

● Fine-tune Kp and Ki until smooth heater control is reached.


Document Feedback CCS801 Sensor Measurement Control


4 Sensor Measurement Control

The gas dependent resistance of the MOX sensing layer is typically measured using a simple voltage

divider (Figure 4) comprising of the sensor resistance (Rs), a series load resistor (RL) and an

Analogue-to-Digital Converter (ADC).

Rs = RL * Vadc/ (VDD – Vadc)

An ADC input with an effective bit resolution of at least 10 bits (ENOB) is required; a higher bit

resolution is more desirable to measure the sensor resistance. Oversampling may be used to increase

the effective number of bits, if a fast ADC is chosen. The ADC sampling rate should be at least 10

kHz. A buffer is optional but advised if the ADC input impedance is

Document Feedback CCS801 Hardware Design Considerations


5 Hardware Design Considerations

The recommended application circuit for CCS801 is shown in Figure 4.

In this section, Electrical and Electronic (EE) block diagram, components selection and PCB layout

design information is presented to ensure optimum performance and to reduce the design-in cycle

time for customers. Meanwhile, Schematic, EE Bill of Materials (BOM) and PCB layout for CCS801

Development V4 board are included for customers’ reference.

5.1 EE Block Diagram

Figure 4 illustrates the EE block diagram. The recommended application circuit for CCS801 consists

of one CCS801 sensor, one MCU, two operational amplifiers as voltage buffers, one P-CH MOSFET,

one 39Ω with ±1% tolerance resistor (R1), one 200kΩ with ±1% tolerance resistor (RL) and C1, C2 and

C3 decoupling capacitors.

Figure 4:

EE Block Diagram

The entire system including the MCU, is working with +3V3 operating voltage. The MCU firmware

controls the heater RH, measures the sensitive layer RS, and optionally communicates with some host

systems by +3V3 I2C bus. It provides

● DC voltage (range from 0.0V to +3.0V) to OP AMP #1 by 12 bits DAC port to regulate the power

supplied to heater.




● One GPIO port is configured as output to control P-CH MOSFET ON/OFF. When ON,

+3V3_VDD power can directly pass through RL and RS to GND. GPIO output with high logical

level is to turn off the MOSFET and with that powers off RS, in contrast, GPIO output with low

logical level will turn on MOSFET and with that powers on RS.

● Two 12 bits ADC ports, which will measure in real time URH and URS voltage by OP AMP #1 and

OP AMP #2 voltage buffers individually.

OP AMP #1 acts as

● DAC voltage buffer

● Providing enough current and voltage to the low-ohmic resistor load (RH+ R1) through op amp

output voltage VOUT

OP AMP #2 acts as

● URS voltage buffer

● Isolating the URS_ADC port of the MCU from the CCS801 sensor resistance RS so that the input

impedance of the ADC port does not affect URS voltage measurement

Figure 5 shows: without op amp used, finite input impedance RIN of URS_ADC port will be in parallel

with RS. The equivalent resistance Req will thus be less than RS. As a result, the URS voltage will be

not the actual voltage across RS.

Figure 5:

How Input Impedance of ADC Port Affects URS Voltage without OP AMP#2

P-CH MOSFET is a switch to enable or disable DC current through the sensor resistor RS from

+3V3_VDD power rail. The MOSFET is controlled by a GPIO port.

The section 5.2 will describe in detail how to select the components, which include OP AMP, MCU, P-

CH MOSFET, R1 / RL.




5.2 Selection of Components

5.2.1 OP AMP Selection

The following parameters are relevant when selecting an op amp for CCS801 application circuit, an op

amp type with rail-to-rail input/output is preferred.

Three key parameters should be considered when selecting the op amp:

● Input Bias Current (IB) for URS voltage buffer (OP AMP #2)

● Headroom (OP AMP #1)

● Output current capability (OP AMP #1)

1. Input Bias Current (IB) for URS Voltage Buffer (OP AMP #2):

Figure 6:

URS Voltage Produced due to Input Bias Current (IB)




Figure 7:

URS Voltage Produced due to Input Bias Current (IB)

Depending on the type of input transistor used in op amp design, the input bias current magnitudes

can range from μA down to pA. Figure 6 indicates an op amp using bipolar junction transistor (BJT)

technology. It is recommended to select an op amp with a max input bias current of 10pA.

The reason is (refer to Figure 6 and Figure 7): when GPIO is high level to turn off MOSFET (system

being idle mode), input bias current IB will pass through CCS801 sensor resistor RS to GND so that

URS will produce a voltage (=IB* RSCOLD) to potentially damage sensor if at that time URS is higher than

100mV and working with such way for a long time.

2. Headroom (OP AMP #1):

In reality, the op amp output voltage cannot reach the power rails VDD level. The difference between

the output voltage and the rail VDD is called headroom as shown in Figure 8,

(1) When VOUT → VDD: VDD – VOUT = VOH

(2) When VOUT → VSS: VOUT – VSS = VOL




Figure 8:

A Typical Output Stage of OP AMP

For the CCS801 application circuit, the max headroom VOH for the DAC voltage buffer (OP AMP #1)

should be equal to or less than 300mV at 30mA load. Figure 9 is a headroom vs load current curve

example, if the datasheet does not indicate such a curve, ask the supplier to provide it. From this

curve, headroom VOH will be 300mV at 30mA current load.

Figure 9:

A Typical Curve of Headroom vs Load Current

3. Output Current (OP AMP #1):

For CCS801 application circuit, DAC voltage buffer (OP AMP #1) should have enough output current

and voltage for low-ohmic resistor load. According to the CCS801 datasheet, the heater resistance RH

is in between 50 ~ 66Ω at URH = 1.4V @ 50% relative humidity. The DC current through heater RH will

be in the range of 21.3~28mA. Considering R1 (39Ω) in series with RH, the op amp output voltage

should be between +2.23~+2.49V at URH 1.4V and the op amp output voltage should be between

+2.55~+2.85V at URH 1.6V (refer to Figure 10).




Figure 10:

OP AMP Output Voltage Requirements

URH(V) R1(Ω) RH(Ω) OP AMP Output Voltage Requirement(V)

Min Max

1.4 39 50 66 2.23 to 2.49

1.6 39 50 66 2.55 to 2.85

For DAC voltage buffer (OP AMP #1), in order to guarantee the system circuit can work properly with

enough design margin, two conditions must be met:

(1) Should support min 30mA resistor load

(2) Headroom VOH should be ≤ 300mV to make sure that output voltage of op amp can reach +3.0V

output.

You can select one op amp with dual channels for URS and URH, or select two single-channel op

amps for URS and URH individually according to the above requirements.

5.2.2 MCU Selection

The recommended MCU requirements to support the CCS801 sensor configuration and MOX

software libraries is listed below:

● 8-bit or 16-bit architecture

● Ability to access milliseconds (clock or timer)

● Supports +3V3 operating voltage

● Flash memory size: 32kBytes with 1kByte E2PROM 1

● RAM size: 2kBytes 1

● Supports 12bits ADC/DAC, GPIO

Software libraries containing proprietary algorithms and example Android applications are available for

indoor air quality. Please refer to ENS MOX Library API reference guide for more information.

5.2.3 P-CH MOSFET Selection

When selecting P-CH MOSFET, the following specification should be followed,

● Min drain current ID: 100mA

● Drain-source on-state resistance RDSON: max 120mΩ

1 There might be an external host, and then I2C needs to be implemented. Or the rest of the application runs on this MCU, and then more FLASH and RAM is needed.




● Turn-on delay time td(on): max 15ns

● Output capacitance Co: max 200pF

5.2.4 R1/RL Selection

● R1: nominal value is 39Ω with power rating 1/16W and should use at least ±1% tolerance to

make sure to get more accurate URH voltage reading. ±0.5% or ±0.1% tolerance is preferred.

● RL: nominal value is 200K with power rating 0.01W or more and should use at least ±1%

tolerance to make sure to get more accurate URS voltage reading. ±0.5% or ±0.1% tolerance is

preferred.

5.3 Development Board Details

5.3.1 PCB Layout Consideration

For CCS801, it is cost-effective to use a 2-layer PCB stack-up. If PCB size is a limiting factor, the

suggested 4-layer PCB stack-up is: top (L1), GND plane (L2), power plane (L3) and bottom (L4). For

components placement and PCB layout, refer to PCB guideline(s) from individual part supplier.

5.3.2 CCS801 Development Board V4 Schematic

The CCS801 Development V4 board is developed for evaluation of the CCS801 sensor.

The highlighted three red blocks in Figure 11 are the optional PWM implementation only required in

case the MCU does not have a DAC available, which is not covered in this application note.

U3 is a STM MCU (Part Number: STM8L151G6U6), U4 is an Analog Devices two channels op amp

(Part Number: AD8656), P2 is 4 pins with 2.54mm pitch solder pad for firmware programming and

debugging, U1 is an ams ENS210 relative humidity/ temperature sensor, U2 is an ams CCS801 VOC

sensor, Q1 is a NXP P-CH MOSFET (Part Number: NX2301P), P1 is 2 rows 4 pins with 1.27mm pitch

connector to communicate with ams USB-I2C dongle. R3 and R2 in schematic are for R1 and RL

individually in the above EE block diagram.




Figure 11:

CCS801 Development V4 Board Schematic




5.3.3 EE Bill-of Materials

Table 12 :

CCS801 Development V4 Board EE BOM

Ref Designator

Quantity(PCS)

Manufacturer Manufacturer Part Number

Parts Description

U4 1 Analog Devices Inc.

AD8656ARZ-REEL7 IC OPAMP GP 28MHZ RRO 8SOIC

U3 1 ST Micro STM8L151G6U6 IC MCU 8BIT 32KB FLASH 28UFQFPN

U2 1 ams CCS801 Gas Sensor

U1 1 ams ENS210 Temp and Humidity Sensor

R12, R13 2 Yageo RC0402FR-07100KL RES SMD 100K OHM 1% 1/16W 0402

R8, R9 2 Yageo RC0402FR-07100KL RES SMD 100K OHM 1% 1/16W 0402

R7 1 Yageo RC0402FR-07100RL RES SMD 100 OHM 1% 1/16W 0402

R6 1 Yageo RC0402FR-07270RL RES SMD 270 OHM 1% 1/16W 0402

R4, R10 2 Yageo RC0402JR-070RL RES SMD 0 OHM JUMPER 1/16W 0402

R3 1 TE Connectivity CPF-A-0603B39RE RES SMD 39 OHM 0.1% 1/16W 0603

R2 1 Yageo RC0603FR-07200KL RES SMD 200K OHM 1% 1/10W 0603

R1 1 Yageo RC0402JR-0710KL RES SMD 10K OHM 5% 1/16W 0402

Q2, Q3 2 ON Semiconductor BSS138LT1G MOSFET N-CH 50V 200MA SOT-23

Q1 1 NXP NX2301P,215 MOSFET P-CH 20V 2A TO-236AB

P1 1 GCT (GLOBAL CONNECTOR TECHNOLOGY)

BD030-08-A-A-0200-0300-L-G

1.27mm pitch BOARD-BOARD CONNECTOR HEADER, 8WAY, 2ROW

D3 1 Kingbright APHHS1005CGCK LED GREEN CLEAR 0402 SMD

D2 1 Kingbright APHHS1005SURCK LED RED CLEAR 0402 SMD

D1 1 Littelfuse SP3021-01ETG TVS DIODE 5VWM 14.7VC SOD882

C10, C11 2 Yageo CC0402KRX7R7BB562

CAP CER 5600PF 16V X7R 0402

C6 1 Murata GRM155C80J106ME11D

CAP CER 10UF 6.3V X6S 0402

C2 1 Murata GRM155R61C105KE01D

CAP CER 1UF 16V X5R 0402

C1, C3, C4, C7, C8

5 AVX Corporation 0402ZD104KAT2A CAP CER 0.1UF 10V X5R 0402




5.3.4 PCB Prints

Figure 13 :

CCS801 Development V4 Board PCB Prints


Document Feedback CCS801 Mechanic and Thermal Considerations


6 Mechanic and Thermal Considerations

6.1 Sensor Placement and Ambient Exchange

The CCS801 gas sensor DFN package has been designed to expose the sensing element to the air

within the package cavity. Exchange of air takes place via the package opening(s) so the

environmental air, outside the enclosure, needs to reach the package. Therefore, an exchange of air

within the enclosure and the environment needs to take place. The response time of CCS801 depends

on the efficiency of this exchange which creates some design considerations as follows:

● The exchange is more efficient if a flow of air is permitted, therefore, inlet and outlet apertures

are preferred

● The air flow path should pass over the CCS801 gas sensor package opening(s)

● Close proximity of the CCS801 gas sensor to the environment prevents any unnecessary delay

● Aperture diameter to depth aspect ratios should ideally be 1:1 or greater

● Any filter membranes should not unnecessarily impede the flow of air

● Any materials used in the product construction should not adsorb or desorb gases of interest as

this will impact the accuracy of the measurement

● Any cavities formed around the CCS801 gas sensor should be as small as possible to reduce

the “dead volume”

● Existing apertures, for example, USB connectors, speakers, microphones etc. may be utilized

for the purposes of exchange.

6.2 Relative Humidity and Temperature Compensation

The CCS801 sensor output will be impacted by environmental factors such as ambient temperature

and relative humidity. Air quality results can be compensated for environmental changes by using a

relative humidity and temperature sensor with high accuracy and a fast response time such as the

ENS210. It is recommended that the ENS210 is placed in the same cavity as the gas sensor,

CCS801. Please refer to AN000391 for ENS210 design guidelines.

Sensor data from ENS210 can be written to CCS801 by the host system and used to compensate for

relative humidity and temperature changes. Please refer ENS MOX Library API reference guide for

more information for the software libraries for CCS801.

6.3 Thermal Considerations

The CCS801 has a fixed power heater drive. This means if it is operated at higher or lower ambient

temperatures this could have an impact on the heater temperature. This needs to be considered when

designing a product is there can often be many heater sources on PCBs. In a smartphone for example

there is the main application processor, connectivity devices, power management ICs and RF




amplifiers etc. The CCS801 gas sensor is also a source of heat, all of these components together will

cause local fluctuations in the ambient air temperature inside the product.

Therefore, best practice should be employed to provide thermal isolation around the CCS801 gas

sensor which creates some design considerations as follows:

Thermal convection

● Baffles to separate other heat source components from the gas sensor should be built into the

enclosure

● Similarly, suitable ventilation should be employed

Thermal radiation

● The sensor should be shielded from direct line of sight with radiant heat sources

Thermal conduction

● Maintain maximum possible layout separation between other component heat sources and

CCS801 gas sensor

● Copper planes should contain discontinuities between other heat source components and the

CCS801 gas sensor

● The exposed pad on CCS801 should be bonded to a suitable PCB copper plane to improve device

cooling

Forced air cooling

● Provide baffles in the flow of air to slow the air before it reaches the sensor

● Offset the package opening(s) from the enclosure aperture to prevent direct cooling




6.4 Implementation Examples (for illustration purpose only)

Sensor ID

Mechanical Thermal

Pros Cons Pros Cons

1

● Large apertures

● Sensor close to aperture

● Sensor in air flow

● Large dead volume ● Discontinuous

copper with heat source

● Close to heat source

● Cavity shared with heat source

2

● Large apertures


● Sensor out of air flow

● Large dead volume

● Continuous copper with heat source



3

● Aperture directly over the sensor


● Aperture over sensor will require filter membrane

● Small aperture

● Single aperture

● Continuous copper with heat source



● Sensing element in direct air flow path

4 ● Large apertures


● Sensor far away from aperture

● Large dead volume

● Far from heat source ● Continuous copper with

heat source

5


● Small dead space

● Small aperture

● Single aperture

● Discontinuous copper with heat source

● Cavity separate to heat source

6

● Large apertures



● Small dead volume

● Separate PCB to heat source

● Cavity separate to heat source

2

AP(heat source)

1

4

5

6

3


Document Feedback CCS801 Product Assembly and Materials


7 Product Assembly and Materials

The product assembly and the materials used should be managed based on the criteria outlined in the

CCS801 assembly guidelines, please refer to application note AN000364 for more information.


Document Feedback CCS801 Summary


8 Summary

This document explains the CCS801 operating mode, heater control/sensor measurement control and

how to implement the recommended application circuit for CCS801, including components selection

and PCB layout design to ensure optimum performance. It also includes the ams CCS801

Development V4 board as a reference design. Mechanical/thermal consideration, product assembly

requirement are covered. This when followed correctly will result in reducing the design-in cycle time

and providing optimal performance for CCS801 designs.


Document Feedback CCS801 References


9 References

Document Reference Description

CCS801_DS000457 CCS801 Datasheet

CCS801_AN000364 CCS801 Assembly Guidelines Application Note


Document Feedback CCS801 Revision Information


10 Revision Information

Changes from previous version to current revision v3-00 Page

Initial Cambridge CMOS Sensors version 1-00

Version 2-00

Version 3-00: add closed-loop solutions for hardware and firmware implementation All pages

● Page and figure numbers for the previous version may differ from page and figure numbers in the current revision.

● Correction of typographical errors is not explicitly mentioned.


Document Feedback CCS801 Legal Information


11 Legal Information

Copyrights & Disclaimer

Copyright ams AG, Tobelbader Strasse 30, 8141 Premstaetten, Austria-Europe. Trademarks Registered. All rights reserved. The material herein may not be reproduced, adapted, merged, translated, stored, or used without the prior written consent of the copyright owner.

Information in this document is believed to be accurate and reliable. However, ams AG does not give any representations or warranties, expressed or implied, as to the accuracy or completeness of such information and shall have no liability for the consequences of use of such information.

Applications that are described herein are for illustrative purposes only. ams AG makes no representation or warranty that such applications will be appropriate for the specified use without further testing or modification. ams AG takes no responsibility for the design, operation and testing of the applications and end-products as well as assistance with the applications or end-product designs when using ams AG products. ams AG is not liable for the suitability and fit of ams AG products in applications and end-products planned.

ams AG shall not be liable to recipient or any third party for any damages, including but not limited to personal injury, property damage, loss of profits, loss of use, interruption of business or indirect, special, incidental or consequential damages, of any kind, in connection with or arising out of the furnishing, performance or use of the technical data or applications described herein. No obligation or liability to recipient or any third party shall arise or flow out of ams AG rendering of technical or other services.

ams AG reserves the right to change information in this document at any time and without notice.

RoHS Compliant & ams Green Statement

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Content Guide1 Introduction2 Operating Modes3 Heater Control3.1 Calibration3.1.1 Cold Resistance Measurement

3.2 Heater Measurements and Control3.3 PI Control

4 Sensor Measurement Control5 Hardware Design Considerations5.1 EE Block Diagram5.2 Selection of Components5.2.1 OP AMP Selection5.2.2 MCU Selection5.2.3 P-CH MOSFET Selection5.2.4 R1/RL Selection

5.3 Development Board Details5.3.1 PCB Layout Consideration5.3.2 CCS801 Development Board V4 Schematic5.3.3 EE Bill-of Materials5.3.4 PCB Prints

6 Mechanic and Thermal Considerations6.1 Sensor Placement and Ambient Exchange6.2 Relative Humidity and Temperature Compensation6.3 Thermal Considerations6.4 Implementation Examples (for illustration purpose only)

7 Product Assembly and Materials8 Summary9 References10 Revision Information11 Legal Information

Documents

CCS801: Application Note (English) - ScioSense › wp-content › uploads › 2020 › ...divider circuit. The micro-heater (R H) will be heated up very quickly with supply voltage