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ADS131E08: DVDD rail is shorting at boot up

Jack Erdozain
Prodigy 20 points
Part Number: ADS131E08


Hello, I’ve designed a custom board which uses the ADS131E08 for measuring simultaneous current and voltage measurements. Unfortunately I am running into issues, the DVDD which is attached to 3.3V rail (LDO on board) is effectively shorting. We are yet to couple it to any digital system to bring up the SPI, so the SPI inputs are floating.  I’ve tried a couple of tests to diagnose the issue:

Disconnected the LDO and connected to an external lab supply: still shorts (LDO unloaded provides correct voltage)
Disconnected the ADC from analog inputs (removed R116 -R138): DVDD still shorts
Removed R117: DVDD still shorts


I would love feedback on if there are any obvious error in the schematic that could cause the issues that I am seeing or any test procedures I could follow to diagnose. Thanks so much for your support! 



  • 0
    TI__Guru 53676 points

    Hi Jack Erdozain,

    I am confused as to what you are asking from us - are you looking for help trying to identify the short? Is it possible that the board has a solder short somewhere, or that the board wasn't cleaned well after assembly? Nothing on your schematic looks obviously wrong such that it would cause this issue, assuming you've met the dropout voltage on the LDOs

    How are you determining that DVDD is shorted?

    -Bryan

  • 0 in reply to Bryan Lizon86
    Prodigy 20 points

    Hi Bryan, 

    Sorry for the unclear post, and thanks for the swift response! I was mostly looking for feedback on the schematic to ensure something is not misconfigured in the design. We have multiple boards all exhibiting the same behavior so I don't believe it's an assembly error, but more likely an error in the design. The board fab quality looks good (assembled professionally, without any observable stray solder, well cleaned).

    The short (or at least excessive power draw through DVDD) was diagnosed by observed excessive power draw on the rail, drooping the LDO. With the board off, I'm measuring sub 1 ohm resistance between DVDD and GND.  Another note is that the chip is heating up. All of this leads me to believe that something might be wired incorrectly in the schematic.

    Thanks again 

  • 0 in reply to Jack Erdozain
    TI__Guru 53676 points

    Hi Jack Erdozain,

    Is R117 installed by default on your board? I.e. when you powered all of your boards originally your net "PP5V3 Sense" is directly connected to your net "ADC1 LDO SNS EN"? You mentioned in your original post that you removed R117, which implies it was installed by default, by I wanted to confirm

    The GPIO inputs on the ADS131E08 are referenced to DVDD and cannot tolerate a voltage > DVDD +0.3 or they can sustain permanent damage

    -Bryan