• State TI Thinks Resolved
  • Locked Locked
  • Replies 4 replies
  • Answers 3 answers
  • Subscribers 33 subscribers
  • Views 848 views
  • Users 0 members are here
Support feedback
Options
Options
Related

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

LMH1981 input HUM noise

Toshi
Expert 1780 points
Other Parts Discussed in Thread: LMH1981, OPA615

HI 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.