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CC2640R2F: CC2640R2F ADC Gain Error Anomaly After 85°C/90% RH Reliability Test (Single Unit)

Mike Wu1
Genius 3271 points

Part Number: CC2640R2F

Dear TI Team, (or replace with the specific AE's name)

We have a customer utilizing the CC2640R2F in their end product (a battery tester). During their recent product reliability testing, they observed an anomaly regarding the ADC reading accuracy. We are reaching out to seek your technical support and recommendations on this issue.

Below is a summary of the system background and the observed anomaly:

[System Background & Application]

  • End Application: Battery tester. The CC2640R2F ADC is used to measure external battery voltage (measurement range: 4V to 31V).

  • Hardware/Software Architecture: The hardware utilizes a voltage divider network and an operational amplifier (OPA) to step down the high voltage to an ADC-acceptable range. On the software side, initial calibrations have been implemented to compensate for hardware component tolerances (e.g., resistor variations, OPA offset errors), ensuring that the accuracy meets product specifications at room temperature.

[Anomaly Description]

  • Test Conditions: High Temperature/High Humidity (Damp Heat) at 85°C / 90% RH. Measurements were taken after the units returned to room temperature.

  • Sample Size: 5 prototype units (each containing one CC2640R2F).

  • Observed Issue:

    • After returning to room temperature, 4 out of the 5 units maintained ADC measurement accuracy within specifications.

    • However, 1 unit exhibited a significant error amplification.

    • Characteristics: For voltages below 14V, the accuracy remains within spec. However, for voltages above 14V, the error exceeds the specification, and the error increases proportionally as the measured voltage gets higher. This behavior strongly resembles an ADC Gain Error or a drift in the internal Reference Voltage (Vref).

[Assistance Required from TI]

We would greatly appreciate it if you could help evaluate this phenomenon and provide further analysis and debugging recommendations. Your guidance will be highly valuable for us to assist the customer in resolving this issue.

Thank you very much for your support!

Best Regards,

Mike1

  • 0
    TI__Guru**** 171839 points

    Mike, 

    I am not entirely sure if the assembly might have damaged the device package and the damp heat compounded to manifest this issue.

    In this case, I would ask the customer to create a larger sample size and observe the amount of failures. This may expose a trend to allow further investigation on this issue. 

    I would also check other factors such as insufficient solder underneath the device (the humidity might accumulate under the device and create leakage paths), solder paste type and compound and other assembly factors. Naturally, doing an automated assembly is always preferable. 

    I will try to think about additional aspects that might be influencing this scenario and report back. 

    Regards,

    Rafael

  • 0 in reply to desouza
    Genius 3271 points

    Hi Rafael, 

    Thanks for your  comment, I will let my customer to create a larger sample size and observe the amount of failures.

    Mike