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LM139AQML-SP: PSRR

JDJ
Expert 3171 points
Part Number: LM139AQML-SP
Other Parts Discussed in Thread: LM139

For the LM139AQML-SP the PSRR in the datasheet is listed as 60dB. Is there a graph that indicates the PSRR at a specific frequency. 

My frequency is 100kHz and want to ensure that the 60dB still fits that frequency. 

Thanks,

Jack

  • 0
    TI__Guru 50016 points

    Hi Jack,

    We do not have data for PSRR over frequency. A comparator does not have a linear output like an op-amp, so testing over frequency is VERY, VERY difficult and problematic.

    The PSRR given is for DC. If we assume the PSRR first pole is also 60dB at 1Hz, then assuming a single pole rolloff of 20dB/decade, the 0dB point would be 1kHz, so it is critical to have clean supplies. This is true of any device.

    Luckily, since the LM139 family is open collector, the supply current is fairly stable since it does not supply output current, so it is possible to locally RC (and maybe even L) filter the comparators supply. This would be our recommendation as the specifications are assuming a clean supply.

  • 0
    Guru 140200 points

    Hi Jack,

    contact us, if you need help with the RLC filter :-)

    Kai

  • 0 in reply to kai klaas69
    TI__Mastermind 23425 points

    I am closing this post since Jack stated that Paul's answer resolved his questions.

    Chuck