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AMC3330-Q1: High voltage sesning circuit ripple voltage issue

Hardik Sanepara
Prodigy 40 points
Part Number: AMC3330-Q1
Other Parts Discussed in Thread: OPA333

Hi Team,

Please find the following circuit that we are using for high voltage measurement  (Please see attached image ). wherein we are getting analog output ripple with around 33mV to 45mV ( Please see attached image of results)

Input voltage raneg is 0V to 1000V.

we need your help to identified why the ripple is that much high ? Please advise.

we are expecting less than 8mV of ripple. please advise us for the same.

regards,

Hardik

  • 0
    TI__Mastermind 49111 points

    Hi Hardik,

    Where are you measuring this signal in your schematic? 

    Can you provide a picture of the layout? 

    Can you please probe both the positive and negative output of the AMC as well as the SE output from the OPA at the input of the ADC?

    Can you explain why you expect 8mV of ripple? 

    R934 and R935 voltage dividers should not be necessary, if you want to adjust the gain, it can be accomplished using Rf and Rg in the OPA stage. Can you please explain why this configuration was chosen? 

  • 0 in reply to Alexander Smith
    Prodigy 40 points

    Hi Alexander,

    we measured the voltage at C523. 

    We measured the voltage at at OUTP and OUTN pin of AMC. observed the almost same as C523 noise observed.

    our target ripple is 8mV, because we are measuring -1000V to 1000V with 12Bit ADC at 3.3V. small voltage ripple is impacting a lot in actual measurement.

    Its difficult to share the PCB layout.

    Regards,

    Hardik

  • 0 in reply to Hardik Sanepara
    TI__Mastermind 49111 points

    Hi Hardik,

    If the noise is present on both OUTP and OUTN, then I would expect it to be largely canceled out by the CMRR of the OPA333. 

    How about the 3.3V power supply?

    R934 and R935 voltage dividers should not be necessary, if you want to adjust the gain, it can be accomplished using Rf and Rg in the OPA stage. Can you please explain why this configuration was chosen?