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AMC1200: AMC1200B Output when VDD1 is not present

Alfred Logico
Expert 5250 points
Part Number: AMC1200


Hi Team,

I received an inquiry from my customer on the AMC1200B. What will be the Output Voltage on VOUTP and VOUTN if only VDD2 is present (3.3V).VDD1 is Zero volts. Assuming the differential voltage on the inputs VINP and VINN can vary from 0 to 250mV. 

Also please consider two cases below:

  1. VDD1 always zero but VDD2 has proper bias and there are input signals on VINP and VINN
  2. VDD1 and VDD2 initially have good steady-state bias, then VDD1 is removed while the VINP and VINN signals are present

 

     We are interested to know what kind of VOUTP and VOUTN signals we will see – what levels and if these are consistent or bound what voltage level.  This way, the DSP receiving the VOUTP and VOUTN signals can manipulate this and/or ignore if there is no valid input-side bias

Thanks! 

Best Regards, 

Alfred

  • 0
    TI__Guru 56442 points
    Hi Alfred,

    Thanks for your post!

    The differential VOUT can be either full scale positive or negative in the event of VDD1 failure, this device does not have a defined fail-safe mode.

    This post may help: e2e.ti.com/.../2476192
  • 0 in reply to Alexander Smith
    TI__Expert 5250 points

    Hi Alexander,

    Here is the feedback of my customer:

    I think full range positive/negative are the worst case swing.  From our observation, we’re getting voltages in between – meaning the stuck level is not guaranteed and can vary between full range positive/negative.

    Or, the resulting differential from L and N ADC inputs, if these are on full range positive/negative results to the stuck value that we’re getting.  We can bring out these ADC values and compare it with the differential.

    I just want to confirm if it just goes to two modes:  either full scale positive or full scale negative and no voltage somewhere in between?

    Thanks! 

    Best Regards,

    Alfred Logico

  • 0 in reply to Alfred Logico
    TI__Guru 56442 points

    Hi Alfred,

    Give me a couple days and I'll test this thoroughly.