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ADS7142-Q1: Getting wrong values on Channel-2 at -40degC Ambient Temp.

Sunil Dhaduk Dhaduk
Prodigy 30 points
Part Number: ADS7142-Q1
Other Parts Discussed in Thread: ADS7142

Hi Team,

We have used ADS7142QDQCRQ1 part in our automotive product design and we are testing the product at -40degC Ambient Temp.

At that time, we are getting wrong sampled data values on Channel-2 of IC. We are suspecting that ADC's Channel MUX is not working properly at -40degC and ADC is sampling and storing Channel-1 data in Channel-2 Buffer Registers.

Apart from that we have observed that ADC is working properly at -30degC and 0degC Ambient temp. as expected.

We suspect that this issue is with particular Chip Production Batch probably. Please find the chip batch details that we have used in our product as below:

 

MPN

MFR

Country of Origin

Date Code

LOT Code

Issue observed at -40degC

ADS7142QDQCRQ1

TI

THAILAND

JUN-2019

9197324UT2

No

ADS7142QDQCRQ1

TI

THAILAND

1947

9217777UT2

Yes
  • 0
    TI__Mastermind 24940 points

    Hello,

    Apologies for late response. 

    While taking temperature measurements, are all other compents working as expected? connections cables are not exposed and have solid connections?

    Is it possible that anything in the set up could be affected by the temperature change? 

    Has the set up resulted in expected performance with other devices from the same lot, or are all devices from the noted result in unexpected results?

    Regards

    Cynthia 

  • 0 in reply to Cynthia
    TI__Mastermind 24940 points

    This is being address directly. Thank you, Cynthia

  • 0
    Prodigy 30 points

    Hi Cynthia,

    We found the issue with ADS7142 internal auto offset calibration process that is taking more time at -40C during power on. During this period, we were configuring the ADC IC but ADC IC was not responding as it was busy in doing offset calibration process. As we are not monitoring BUSY/nRDY pin of ADC Chip, we are unable to find the actual status of ADC whether it is available to configure or not.

    After adding some delay before configuration, we were able to configure ADC in the right way.

    But here, question is that we haven't found such issue in past with same ADC at -40C. The only difference is the lot number of ADC.

    Could you please let us know whether this could be the probable issue or not?

  • 0 in reply to Sunil Dhaduk Dhaduk
    TI__Mastermind 24940 points

    It is good practice to monitor the BUSY pin. The offset timing is not characterized, thus it can vary, in particular with changing elements such as temperature.