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Ovefrragile channel 1 on ADS1274(8)

user4551715
Prodigy 130 points
Other Parts Discussed in Thread: ADS1274, ADS1278

Recently, a few of either ADS1274 or ADS1278 have been employed in my application.

Unluckily, the channel 1 are all burned, and channel 2 and 3 still work, during low temperature test(-20C), the IOVDD(1.8V) is supplied by TLV7111833D

Does anyone meet the similar situation, or be gladly to share some experience, please inform me.

  • TI__Guru 66906 points
    Hello,

    Thanks for your question. I have a few follow up questions that will help us better understand what is causing the failure.

    Can you tell us more about the device configuration (i.e. power supplies, mode, clock inputs, etc.) and the channel input conditions during your tests?

    Also, what symptoms are you noticing with Channel 1 that indicates a failure (i.e. does the output become all 0xFFFFFF?)?

    In the past, I know that some customers have experienced failing channels when the power-on sequence does not meet the datasheet requirements. Can you please share that information as well?

    Best Regards,
  • in reply to Ryan Andrews
    Prodigy 130 points

    Hi

    The configuration on my circuit is suggested by the typical application in the datasheet, mode is set as high resolution(01), data format is set as SPI Discrete(010), Channel 1~3 are functional by pull up the PD pins

    When the Channel 1 failed, the output of Channel 1 becomes 0xFFFFFF as you mentioned, however, Channel 2 and 3 are both functional.

    We guess the voltage noise of DVDD may cause the problem, TLV7111833D has been tested in the formal experiment, now we switch it with TPS79418 to be tested, moreover, we switch the Channel 1~3 to Channel 2~4, to avoid the unexpected problem.

    Plus, an additional application problem we have recommended to ti.com, that is, the PD pin of Channel1 is pulled low, whether the TDM mode still functional, waiting for their answer

  • in reply to user4551715
    TI__Guru 66906 points

    Thanks for the additional information.

    Did changing the IC for the DVDD power supply solve the issue consistently? I'm not intimately familiar with either device, but at a glace it appears that either one should work.

    user4551715 said:
    Plus, an additional application problem we have recommended to ti.com, that is, the PD pin of Channel1 is pulled low, whether the TDM mode still functional, waiting for their answer

    Did you post another question somewhere else on the forum? If you're asking whether TDM Mode can still work when Channel 1 is powered-down, the answer is "yes." The TDM data format has two options: "fixed" or "dynamic" data position. If "fixed," then DOUT will output all channels and replace any powered-down channel will all 0's. If "dynamic," then DOUT will only output the channels which are powered-on.

    If that does not answer your question about using the TDM data format, please provide a link to your other post. Thanks!

    Best Regards,

  • in reply to Ryan Andrews
    Prodigy 130 points
    Hi Andrews

    the change of power IC has just been designed and the PCB is now printing, so, i sincerely hope the problem could be solved completely.

    the addition querstion has been posted to the tech support of ti.com, not in the community yet. the TDM mode is designed as the backup plan of data trans.

    Best Regards,
  • in reply to user4551715
    TI__Guru 66906 points
    Hello - did this issue get resolved with the new LDOs?

    Regards,
  • in reply to Ryan Andrews
    Prodigy 130 points

    hi

    i solved the problem eventually by change the external power supply.

    a 24VDC(+12V vs -12V) was used as the external supply, an isolation DCDC(MKW3036) is just after the supply port, and a PMIC(ADP5052) and LDO (TPS54928) is used to supply ADS1274.

    When the external supply is 24VDC(+12V vs -12V), the channel 1 on ads1274 is very frragile..

    when the external supply is 24VDC(+24V vs 0), the chip works well.

    it is quite strange... WTF is wrong with the isolation chip...