Version: **

1. Is the XENSIV^TM PAS CO2 sensor affected by acoustic and vibration noise?
   XENSIV^TM PAS CO₂ sensor has a robust packaging, and is acoustically isolated from the surrounding noise. The sensor has been designed in such a way that only CO₂ molecules can diffuse within the measurement chamber, while significantly attenuating the surrounding noise. As shown in Figure 1, the sensor performance remains within the specifications up to 101 dB SPL for pink noise, which is one of the most common signals in biological systems and is widely present in modern-day music.
   Figure 1. Acoustic robustness of XENSIV^TM PAS CO₂
   
   

   Infineon recommends that you isolate the sensor from vibration sources. The operating frequency of the sensor is 40 Hz. If vibration is expected at exactly 40 Hz with very high acceleration (≤ 0.3 g), you should do the following to minimize the vibration impact:

   • Mount the sensor in the X-direction of vibration.
   • Enable the denoiser filter.
   • Operate the sensor in continuous mode.

However, for a typical application, the impact of vibration is minimal. As shown in Figure 2, for a test setup with three sensors mounted on a commercially available air purifier, the test result shows that with the denoiser filter enabled, the sensor is robust against the vibration generated by a different fan of the air purifier.

 Figure 2. Vibration robustness of XENSIV^TM PAS CO₂

For more details, visit the CO₂ sensor website and see the application note, General design in guidelines for XENSIV™ PAS CO2 sensor.

2. How much indoor area can be covered by one sensor for a typical application?
   Even though CO₂ is generated locally, after a certain period, the CO₂ concentration is distributed throughout the room. Therefore, irrespective of the room size and number of people, the sensor is capable of accurately estimating the indoor CO₂ concentration within an indoor environment. For more details, see the application note, General design in guidelines for XENSIV™ PAS CO2 sensor.
   
   
3. Are scientific literature available indicating the harmful effects of CO₂ for human body?
   Several studies have been done on the effect of CO₂ on the human body at various concentration levels. The summary is provided in the chart. See Source [1] for the details of the study.
   
   

   Figure 3. Impact of CO₂ on the human body at various concentration levels

   Source
   

   1. https://www.sciencedirect.com/science/article/pii/S0160412018312807
   2. https://books.google.de/books?hl=en&lr=&id=TEnO6lILSj4C&oi=fnd&pg=PR8&dq=Co2+sensors+and+health&ots=Xy1umDNsmq&sig=ZjljEpPMeRBse75NgUiwbh01KuM&redir_esc=y#v=onepage&q=Co2%20sensors%20and%20health&f=false
   3. https://ieeexplore.ieee.org/abstract/document/8767280

4. Is it possible to obtain MEMS separately from the module along with the compensation software to integrate them into a custom DSP solution?
   No, currently it is not possible to purchase MEMS separately.
   
   
5. How is the sensor calibrated? Does it need recalibration after delivery?
   Each sensor is calibrated in the factory when it is shipped from Infineon. For the final product, you  will not have to perform calibration. However, you should use the automatic baseline offset correction (ABOC) feature during operation to minimize errors due to aging. See the application note, FCS_ABOC_XENSIV™ PASCO2.
   
   
6. How can I generate a known level of CO₂ in ppm?
   CO₂ sources are numerous such as bike tire CO₂ inflators, soda water, and human breath. To arrive at a known level, capture the CO₂ gas in a Tedlar bag and pump it into a gas chamber using a 6-V diaphragm pump. CO₂ concentration can easily reach more than 10000 ppm in such a setup. A reference CO₂ sensor can be used to measure the known level. See the application note, Recommended performance evaluation methodology for XENSIV™ PAS CO2 sensor.
   
   

   One such setup is as follows:
   

7. Can the XENSIV^TM PAS CO₂ sensors be battery-powered?
   XENSIV^TM PAS CO₂ can be used for battery-powered applications. Infineon has a reference design which can help operate the sensor at 3.3 V (a low-cost boost converter circuitry along with the sensor). For details, see the application note,

   XENSIV™ PAS CO2 for low-power application.

8. When is the CO₂ sensor available? Where can I get eval kits?
   

    

   Evaluation kits are already available with major distributors.

9. What are the power requirements of the XENSIV^TM PAS CO₂ sensor?
   The average power consumption to power up the sensor is 29.7 mW. During the measurement phase, the power consumption is 26.4 mW. Infineon provides a power calculator based on Microsoft Excel that helps in determining the average power consumption based on the end application.
   

   Figure 4. Average power consumption

   For more information, see Section 3 of the application note, XENSIV™ PAS CO2 for low-power applications.

10. What is the long-term stability of these sensors?
    

     With the automatic baseline offset correction (ABOC) feature enabled, the sensor accuracy drifts by 1% every year.

    

    Figure 5. Values of pressure and acoustic stability

    See Section 4.1.5 - Transfer function table in the datasheet.

11. How can I reduce a high CO₂ level?
    According to ASHRAE, an ideal living room should not have more than 1100 ppm of CO₂. Therefore, as soon as the CO₂ level increases beyond 1100 ppm, you should ventilate the room.
    
    
12. How is the sensor calibration done?
    
    • Does the sensor calibrate single gas or more gases?
    • How long does the calibration process take?
    • What is the required equipment?
    • How often calibration must be done?
    • Can the calibration be done anywhere or only in the laboratory?
    • Does the sensor have automatic calibration or auto leveling?

Each sensor is calibrated during our production for the complete operating range. Production calibration is done with highly accurate CO₂ gas bottle and verified with an ideal reference sensor.

The sensor might show small amount of offset after assembly due to stress generated from the assembly process on the light source. Therefore, to get the best performance, this offset should be corrected using either FCS or ABOC.

For the FCS calibration, you need to have a reference sensor. In the ABOC mechanism, the device keeps track of the minimum value recorded over a week. The offset to the reference baseline is computed and used to calculate the correction factor to be applied for the week after.

Figure 6. Operation of the ABOC feature

See the application note, After-assembly calibration scheme for XENSIV™ PAS CO2 for more details.

13. Can this device be installed on a microcontroller/system-on-chip such as Arduino/Raspberry Pi?
    Yes. Infineon provides C/C++ libraries for interfacing the sensor.
    See the following GitHub repos:
    
    • For devices compatible with Arduino.
    • For PSoC™ 6 MCU library.

14. Does the response time (T63 = 75s) meet the certification requirements and accuracy for medical applications?
    The sensor is not specifically designed to cover medical applications. However, the response time is defined based on the diffusion process.
15. What are the design rules for integrating the CO₂ sensor into a package for airflow speed and direction?The device must be positioned in such a way that the diffusion of CO₂ molecules can happen easily, with a large enough opening. The recommended opening is at least 14 mm x 14 mm.
    

     

    Figure 7. Airflow direction

 See the application note, General design in guidelines for XENSIV™ PAS CO2 sensor for details.

16. What is the time constant (CO₂) of the sensor?
    Time constant/response time of the sensor is the time it takes to measure the CO₂ concentration. This is due to the diffusion time of CO₂ molecules.
    For VDD3.3 = 3.3 V, VDD12 = 12 V, Tamb = 25°C, % RH = 30 %, p = 1013 hPa, the response time, T63 = 75 seconds.
    See Section 4.1.5 of the datasheet for more information.
    
    
17. What are the response times in different airflows?
    The response time is independent of the airflow. You should not place the sensor directly within the airflow. For more details, see the application note, General design in guidelines for XENSIV™ PAS CO2 sensor.
    
    
18. How do I waterproof the sensor board for wet environments?
    The sensor is not designed for applications where it must be waterproofed. The sensor may be damaged if submerged in water.
    
    
19. Is the CO₂ sensor tested in an environmental chamber?
    A test chamber is used, which  ensures that there is no leakage, and it can maintain laminar flow while exposing the sensor to the target gas concentration. Inside the test chamber, you should accommodate a reference CO2 sensor. Additionally, to get an overview of the complete test conditions, the pressure sensor, humidity sensor, and temperature sensor should also be considered.
    For more information, see the application note, Recommended performance evaluation methodology for XENSIV™ PAS CO2 sensor.
    
    
20. Can the sensor be used within battery-driven consumer goods, with a supply voltage lower than 12V, such as 3.3 V?
    Infineon has addressed the requirement; a reference design is available to ease the design process. You can use this design to realize 12V with relatively low effort. For more information, see the application note, Reference design Sensor2Go kit, and the detailed knowledge base article (KBA).
    
    
21. What are the major technologies used in the sensor?
    The sensor uses a microphone, emitter (MEMS + filter), and the embedded software that implements the sensing algorithm

Note: For more information, see the Community webpage for CO2 sensor where you can find answers to your questions and ask your own.

Version: **

Watchdog timer (WDT) setting is configured with the following three options when the debugger is connected:

  - Counter is stopped when a debugger is connected.
  - Counter is stopped only when a debugger is connected and the CPU is halted during
    a breakpoint.
  - Counter is running when debugger is connected. No reset is issued when the CPU is halted during
    a breakpoint but the counter is not stopped.

Note that in each case, no reset and no FAULT is issued when the debugger is connected to the target system.
For details, see "Debug mode" in the WDT section of the TRM.

Note: This KBA applies to the CYT2, CYT3, and CYT4 series of TRAVEO™ T2G MCUs.

Version: **

Context
Determine the default setting of the watchdog timer (WDT) at power-on.

Solution
TRAVEO™ T2G has two WDTs: basic WDT and multi-counter WDT (MCWDT).
Basic WDT is enabled after power-on, while MCWDT is disabled after power-on.

Note: This KBA applies to the following series of TRAVEO™ T2G MCUs:

• CYT2 Series
• CYT3 Series
• CYT4 Series

References
Refer to the Watchdog Timer section of the TRAVEO™ T2G architecture TRM for more information.

Unexpected debugger disconnection during program execution in TRAVEO™ T2G – KBA233857

Version: **

Solution:

Check if the following operations are performed:

- Check if the JTAG / SWD port has been changed to anything other than JTAG / SWD in the Port settings.

- Check if the following Debug Access Port settings (Disable) are correct.

- CPUSS_AP_CTL register¹:

   DISABLE bit (where xxx can be CM0 or CM4, or SYS)

            ENABLE bit (where xxx can be CM0 or CM4, or SYS)

Note: This KBA applies to the following series of TRAVEO™ T2G MCUs:

• CYT2 series
• CYT3 series
• CYT4 series

¹ For details, refer to "DAP Security" section of the architecture TRM and the "CPUSS_AP_CTL" register of the registers TRM.

Version: **

Question: What needs to be checked if JTAG debugger is not connected?

Answer: If the signal quality of the hardware is not good, do the following:

• Make sure that the JTAG signal wiring on the PCB meets the requirements.
• Check if the JTAG termination circuit is appropriate.

For more information, see the documentation as follows.
AN220270 Hardware Design Guide for the TRAVEO II Family
AN220118 Getting Started with TRAVEO II Family MCUs

Note: This KBA applies to the following series of TRAVEO^™ II MCUs:

• CYT2 Series
• CYT3 Series
• CYT4 Series

Version: **

Question: How do I evaluate the impact of PLL jitter on CAN precision when PLL clock is used for a CAN peripheral?

Answer: Use the following equation to evaluate the impact of PLL jitter on CAN precision:

Where,

•  = The specified PLL clock jitter as the absolute interval (CAN PLL jitter provided in product datasheet)
• NBT = Nominal Bit Time (the inverse of a given CAN bit rate)
• 10 = Maximum bit length during resynchronization guaranteed by bit stuffing in the case of no electrical disturbance. The case where 5-bit dominant continues and 5-bit recessive continues is 10-bit, which is the worst case during normal communication.

The result of df_jitter is the MCU drift equivalent and should be added to the oscillator drift value of the crystal or resonator as shown below:

df_total = df_jitter + df_oscillator

Below shown is an example to verify whether the PLL clock of CYT2B7 Series meets the CAN precision specification.

Example:

• CAN bit rate = 1 Mbps
• PLL Jitter = ±0.75 ns (from PLL Specifications SID345A in the CYT2B7 Series Datasheet)
• Drift of External Crystal Oscillator (ECO):  df_oscillator  = ± 0.01% (generally provided by the crystal supplier)
• Allowed CAN node frequency tolerance: df = ± 0.01%

The 1 Mbps bit rate results in NBT = (1/1 Mbps) = 1 µs. The relative PLL Jitter interval ±0.75 ns results in an absolute interval t_jitter  = ± 1.5 ns.

Therefore, the CAN PLL jitter specification of CYT2B7 meets the CAN specification.

Note: This KBA applies to the following series of TRAVEO II MCUs:

• CYT2 Series
• CYT3 Series
• CYT4 Series

Version: **

Question:
How do I clear the watchdog timer (WDT) in Sleep mode for TRAVEOä II family MCU?

Answer:
The WDT cannot be cleared in Sleep or DeepSleep power modes. To clear the WDT, the CPU needs to wakes up.

In Sleep or DeepSleep power modes, the CPU subsystem is powered-down. The watchdog counter can send WDT WARN ACTION interrupt request to the wakeup interrupt controller (WIC), then WIC wakes up the CPU.

After wakeup, the CPU acknowledges the interrupt request and executes the ISR. The interrupt must be cleared after entering the ISR in firmware. For more details, refer the Watchdog Timer (WDT) section in the Architecture Technical Reference Manual.

Note: This KBA applies to the following series of TRAVEO II MCUs:

• CYT2 Series
• CYT3 Series
• CYT4 Series

Version: **

Question:
What is the thermal resistance for TRAVEOä II CYT2B series?

Answer:
The thermal parameters (Ɵ_Ja, Ɵ_JB, Ɵ_Jc) used to characterize the packages for CYT2B series are shown below.

For example: TVII-B-E-2MB device.

• TQFP-64: Ɵ_Ja = 36.5 °C/W, Ɵ_Jb = 31.5 °C/W, Ɵ_Jc = 7.4 °C/W
• TQFP-80: Ɵ_Ja = 31.7 °C/W, Ɵ_JB = 26.0 °C/W, Ɵ_Jc = 6.2 °C/W
• TQFP-100: Ɵ_Ja = 28.6 °C/W, Ɵ_JB = 20.9 °C/W, Ɵ_Jc = 5.3 °C/W

The above thermal resistance values are also described in the Packaging section of the Datasheet. See the Packaging section for the thermal resistance of other series as well.

Note: This KBA applies to the following series of TRAVEO II MCUs:

• CYT2 Series
• CYT3 Series
• CYT4 Series

Version: **

Question:

Is it possible to use a combination of two different sizes of data fields for buffers/FIFO elements of the CAN FD Controller?

Answer:

No, it is not possible to configure Tx buffer element's data field to different sizes. The CANFDx_CHy_TXESC register allows you to configure the data field size of the Tx buffer element to up to 64 bytes. This configuration applies to all Tx buffers for the respective channel. The same restriction is applicable for Rx buffers/FIFO elements also; different Rx buffer elements belonging to the same CAN channel cannot have different sizes of the data field. The data field size of the Rx Buffer/FIFO elements can be configured through the CANFDx_CHy_RXESC register ('x' is the CAN FD instance number and 'y' is the channel number in the respective CAN FD group).

For more details, see the “CAN FD Controller” section of the Technical Reference Manual.

Note: This KBA applies to the following series of Traveo II MCUs:

• CYT2 Series
• CYT3 Series
• CYT4 Series

Version: **

Question:

How can I get the CPU board to operate only at 3.3 V?

Answer:

Ensure that the jumper settings are as follows:

• J23: Short between pin2 and pin3 (The 3.3 V power rail on the board is enabled).
• J9: Open between pin1 and pin2 (Power-on-reset for +5 V is disabled).

For more information, see the documentation available with the CYTVII-B-E-1M-176-CPU evaluation board.

Note: This KBA applies to the following series of Traveo II MCUs:

• Traveo II for Body CYT2B7 Series