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LM1971 ISSUE

Mickey Zhang
Genius 12080 points
Other Parts Discussed in Thread: LM1971

Hi Team,

The customer is using LM1971. LM1971 can be attenuation step size  from 0dB to -62dB. But when the customer sets LM1971 to be attenuation 0dB, 

the output signal  is more attenuation than the input signal. Look the attachment. The channel 1 is the the input signal and the channel 2 is the output signal.

What is the reason? How to solve the issue?

Thanks,

Best Regards,

  • 0
    TI__Guru* 98965 points
    Hi Mickey,

    Have you tried different attenuation settings? Is the 3-wire serial interface working fine?
    The output is showing different results for different attenuation settings?

    Best regards,
    -Ivan Salazar
    Texas Instruments
  • 0 in reply to Ivan Salazar
    TI__Genius 12080 points
    Hi Ivan,
    Q1:The customer only sets LM1971 to be attenuation 0dB. Does the customer need to set different attenuation?

    Q2: What is the 3--wire serial interface? Are they LOAD pin, DATA pin and CLOCK pin?
    If they are the LOAD pin, DATA pin and CLOCK pin, how does the customer know the 3-wire serial interface is fine?
  • 0 in reply to Mickey Zhang
    TI__Guru* 98965 points
    Hi Mickey,

    I meant to ask if the customer have tried to set a different attenuation level, this is not needed but it could help to see if the problem is present only at a specific attenuation level and to see if the serial communication is working fine so the device is able to set different attenuation settings.
    Yes, 3-wire serial interface are LOAD, DATA and CLOCK pins. Is the customer following the specification on figure 15 on page 8 from the datasheet? If customer tries different attenuation levels and there is a change at the output signal then it could be a sign that the serial communication is working.

    Best regards,
    -Ivan Salazar
    Texas Instruments