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TPS22811: Digital EN control

David Nestler
Prodigy 60 points
Part Number: TPS22811

Tool/software:

I have implemented the following design using TPS22811LRPWR but am unable to enable the 12V0_TEC output.  The way I have it configured, I have a resistor divider to set the nEN/OVLO.  With the 12V input that puts appx 0.9V on this pin.  However, instead of continuing the resistor divider I have connected the EN/UVLO pin to a CPLD at 3.3V logic level.  This way we can enable and disable the 12V0_TEC as we see fit via the CPLD pin.  At startup, the voltage on this pin is 0V until the CPLD writes a logic high (3.3V) at which point I would think both the UVLO and OVLO conditions are met and the device should turn on.  However, when we write 3.3V to this pin, the device will not turn on.  Is this not an acceptable way to implement this?  Do you see any other issue with this schematic that would prevent the device from turning on?

  • 0
    TI__Mastermind 38365 points

    Hi David,

    I don't see any issue with the way in which you are trying to turn on this part. Can you share some waveforms or multimeter reading (at steady state) for all the pins. Also tell me load you are using when trying the startup.

    Best regards,
    Arush

  • 0 in reply to Arush Gupta
    Prodigy 60 points

    Arush,
    Well false alarm, maybe.  I tried a different board and the circuit worked so my guess is that there is some error in assembly or fabrication of the previous board.  I'm a little worried there might be some weird latch condition that happened during power-up or power cycling.  I will try to test again and see if I can recreate any issue but for now it seems ok!  Thanks for your quick response though!