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Internal Vref reading wrong on UCD9224EVM-64

Andrew Seidel
Prodigy 50 points
Other Parts Discussed in Thread: UCD9224, PTD08D210W

Hi,

I am bringing up the UCD9224 eval kit, and when I supply +12V for Vin, the on-die Vref is read as only 1.29V (and 0.64V if I supply +5V).  This locks me out of testing Vout due to false Vin UVLO failure.  I can trick it by setting a really low UVLO trigger, and then Vout operates, but also comes out at a wrong voltage (~2.5V if I set 1V).  The calibration routine locks me out of extreme adjustments (as it should).  Is there something I need to change on the eval kit HW/SW for Vref to be correct, or do I have a bad part?  

Also, for my end design I want to run +5V only, and the silkscreen and part spec say this is ok, but the EVM guide only describes hooking up +12V.  Is there any restriction to use 5V (like will the internal ADCs not have full range unless +12V is supplied?).  Thanks!  Andrew.

  • 0
    Prodigy 50 points

    I ordered a second eval kit and this one reads Vin, etc. just fine, so I had a bad eval board.  Disappointed I never got a reply to this thread, email support, nor my local AE and had to resort to schedule delay and added cost...

    Andrew.

  • 0
    TI__Genius 13700 points

    Unsure why the Vref was low, possibly bypass capacitor was damaged/missing.  I'd really need to see the board to determine the cause.

    About running at lower input voltage, the configuration file that is preloaded in the EVM is set to run from a 12V supply but this can be changed to allow operation from 5V.   The Fusion Digital Power Designer software can be used to adjust these parameters, updating it on the Design page (Update Input Voltage/Write to Hardware/Store to Flash) should update the relative parameters. Refer to the PTD08D210W power module datasheet for its operating limitations, frequency/voltage/power output.