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OPA2330: an issue of configured as Comparator.

Martin Chien
Expert 3590 points
Part Number: OPA2330
Other Parts Discussed in Thread: OPA330, OPA320, OPA196, OPA376, OPA191

Hello Team,

My customer is using OPA2330 and be configured as comparator of a power supply output current monitor, when output current is low enough, OPA2330 output is low; once output current reach a certain level, OPA2330 output should goes high.

However, they found there is 1 units module test failed in production line, after look into it, they found OPA2330 seems has wrong behavior, when IN+ still lower than IN-, the OPA2330 output gets high level, this is the issue they are talking about. please find attached for detail.

Can you help me with reviewing their schematic? anywhere with incorrect design? if the design is correct, should I send it to go FA process?

There is only 1 returned sample, failure rate is around 1/10K.

Thanks a lot for help.

OPA2330 as comparator issue.pptx

  • 0
    TI__Guru 62700 points

    Martin,

    OPA330 is a chopper amplifier and as such should NOT be used as a comparator because pulling the inputs apart prevents the chopper from correcting its inherent input voltage offset (input offset voltage will be in mV instead of microvolts).  Also, OPA330 has back-to-back parasitic diodes between the input terminals (see below) and when the input differential voltage between the inputs is greater than few hundreds millivolts, one of the input diodes will forward bias and disturbed (drag) the threshold voltage resulting in an erroneous tripping point.

     

    Instead, please use an actual comparator, or another non-chopper op amp like OPA320, OPA376, OPA191, or OPA196, which also do not have the back-to-back input diodes.  

  • 0 in reply to Marek Lis
    TI__Genius 11135 points
    Martin

    Did this resolve the issue? If not, post another reply below.

    Thanks
    Dennis