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AFE7920EVM: [URGENT] AFE7920EVM failure upon power-up

Zeljko Jelic
Intellectual 318 points
Part Number: AFE7920EVM

Hi Team,

I have a bit of an urgent request - yesterday when I tried to use our AFE7920EVM board for some tests upon switching on the power supply unit (5 V supply with current limit set at 5 A) I noticed that AFE7920EVM board immediately starts drawing very large current (not at current limit, but about 4 A, and then over next minute this drops slightly to about 3.5 A). There is nothing else connected to the board.

If I try and add the USB cable to the PC, the orange LED is glowing, Latte recognizes the connection, and I can program the LMK without Latte complaining. However, during the bringup procedure last stages, some kind of weird loop is entered where a message pops up saying that some high voltage or value is expected but not detected. This is then retried (high value detection) over and over.

I don't have the exact text message at the moment, as I disconnected the board due to high current draw.

I also tried to manually reset the board by pressing the SW1 reset switch on the board, but there was no impact.

Could you please advise on the proper steps on how to resolve this issue? We have some very strict deadlines soon and we rely on AFE7920EVM for them.

Kind regards,

Željko

  • 0
    TI__Mastermind 23780 points

    Hi Željko,

    While waiting for the device experts to comment, can you measure all power supply rails on the device with a volt meter and report back findings? I suspect one of the supply rails is shorted. Did this board ever work previously?

    Regards, Chase

  • +1 in reply to Chase W
    TI__Genius 10865 points

    Hi Željko,

    As discussed in our virtual meeting, when the DAC output circuit was updated, it has to be ensured that DC bias supply of DAC output pins is not shorted to ground. The DC blocking capacitors were replaced with 0 ohm resistors when you updated this circuit causing this supply to be shorted to ground. That's the reason for high current you noticed. 

    Regards,

    Vijay