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ADS1278-HT: ADS1278HPAP

arif khan1
Intellectual 355 points
Part Number: ADS1278-HT
Other Parts Discussed in Thread: ADS1278

High temperature testing of three parts at 170C fails after 430/640/700 hours. The 1.8V VDD and  3.3V VCCIO power rails are shorting out and drawing excessive current.

As per the data sheet, these parts can run 10,000 hours @ 175C. 

Any ideas what might be the issue.?

Thanks.

-Arif Khan

  • 0
    TI__Mastermind 36240 points

    Hello Arif,

    Have you confirmed that the power supplies are operating correctly at 170C?  If the ABS MAX specs are exceeded, even for a short period of time, this could explain the failure.  Also, if the inputs exceed ABS MAX, this could also show up as excessive current on the power supply pins.

    If you can provide a screenshot of the schematic showing the reference, input amplifier, and power connections around the ADS1278, I will take a look to see if there are any other possible fault paths.

    Regards,
    Keith Nicholas
    Precision ADC Applications 

  • 0 in reply to Keith Nicholas
    Intellectual 355 points

    Hello Keith,

    I will look at the voltages at 170C and see make sure they are within the absolute max limits. 

    Here are the schematics:

    Thanks

  • 0 in reply to arif khan1
    TI__Mastermind 36240 points

    Hello Arif,

    Unfortunately, the pictures did not make it through.  Please save as .PNG file, and then attach by clicking the 'paperclip'.

    Thanks,

    Keith

  • 0 in reply to arif khan1
    Intellectual 355 points

    Hello Keith,

    Is power-on sequencing critical? i.e. the DVDD, IOVDD and theAVDD order? Can latchup be induced? 

    I looked at the evaluation board ADS1x7xEVM-PDK and did not see any power sequencing circuitry on this board.

    Thanks.

    -Arif

  • 0 in reply to arif khan1
    TI__Mastermind 36240 points

    Hello Arif,

    Everything in your schematic looks correct.  The reference, ref buffer, and input amplifiers are all supplied from the same 5V supply.

    An incorrect power-up sequence will not damage the device, or cause a latchup.  The power-up sequence is needed for a proper power-on reset.  If your system does not meet these requirements, you can ensure proper operation by asserting the SYNC pin after device power-on when data first appear.

    For the HPAP package, your approximate theta-ja is 33degC/W.  In High-resolution and High-speed modes, the device can dissipate almost 1W, which means your junction temperature could be quite a bit higher.

    1.  Please confirm which mode, and how much power you are consuming.

    2.  Have you measured the case temperature rise on the part, to ensure you have a good thermal connection to the board?

    If you do not have a good thermal connection, the junction temperature could be much higher than 170C, which may explain the failures.

    Regards,
    Keith