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PGA308: Loss of 1W communication during ESD testing

Alex Favero
Prodigy 10 points
Part Number: PGA308

Hello,

I'm working with a pair of PGA308s that we communicate with using a couple GPIOs of an STM32. During ESD testing we're seeing a loss of communication via the 1W link. Was curious if anyone else with experience with this part had seen this issue or might have a hint or two on what to look for.

Thanks!

  • 0
    Prodigy 10 points

    To clarify, our application does not use the "Three Wire" configuration in which the 1W pin is tied to Vout. We are simply using separate lines for the 1W and Vout pins. See schematic snip below.

  • 0 in reply to Alex Favero
    TI__Mastermind 18347 points

    Alex,

    I have not heard of anyone having this issue with the PGA308.  Is the ESD being applied to the amplifier input, the 1W pin, or general application to PCB?  Do you think there is any degradation in performance (i.e. is the device being damaged)?  If the ESD is applied directly to the 1W pin, I think the ESD pulse may be interpreted as a clock edge and disrupts communications. 

    I know you are using the separate 1W signal (not tied to Vout).  However, in the case where 1W is tied to Vout, there is a 10nF capacitor on the line.  This capacitor is a standard EMC type design approach for pins connected to the outside world.  You may consider adding a 10nF to the 1W output pin.  The EVM is designed to drive the large capacitance and still maintain good communications.  The 1W speed-up circuit on the USB-DAQ-PLATFORM is designed to drive the 1W signal on large capacitances.  I mention this as a standard UART communications probably cannot drive the 10nF without some kind of circuit like the speed-up circuit.  So, if you want to add the capacitance you may need to modify your digital communications.

    Even something simple like a series 1k ohm resistor may help this issue.  The 1k would more likely help protect against damage, but might help with communications issues as well.

    I hope this helps. Best regards, Art