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LMH1981 input HUM noise

Toshi
Expert 1780 points
Other Parts Discussed in Thread: LMH1981, OPA615HI TI, my customer reported that LMH1981 HOUT was failed due to input HUM noise. Do you have a recommended HUM noise filter for LMH1981 ?
  • 0
    TI__Mastermind 32575 points

    I suggest to decrease the value of the input coupling capacitor (Cin) to introduce sufficient voltage droop between Hsync pulses in order to compensate for the worst-case voltage shift due to the AC hum. The proper Cin value will be dependent on the magnitude of the AC hum.

    Alan

  • 0 in reply to Alan O
    Expert 1780 points
    Alan-san, thank you for your help. Well, do you have a minimum Cin value spec(suggstion) ? Also customer find the OPA015 that can reduce a HUM noise. "The OPA615 is a complete subsystem for very fast and precise DC restoration, offset clamping, and low-frequency hum suppression of wideband amplifiers or buffers."(from data sheet). Have you ever use the device at LMH1981 input ?
  • 0 in reply to Toshi
    TI__Mastermind 32575 points
    I suggest Cin value of 10nF or 1nF to see if it can resolve the issue. I have not used OPA615.

    Alan
  • 0 in reply to Alan O
    Expert 1780 points
    Alan, thank you for your help. I've sent the information to customer. Also I've posted OPA615 question to new thread.