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TPA3118D2: Unreliable mute

Michael Combs
Prodigy 20 points
Part Number: TPA3118D2


 I'm having trouble with mute activation on a TPA3118D2. Shutdown is constant high (i.e. amp is always on) and the amp is defaulted to mute with a pullup to 12v on the mute pin. Shorting the pin to ground only activates the mute about 50% of the time. I've now tried 3 different chips, all with the same behavior. I have verified 0v at the pin when shorting to ground, and the amp stays in mute. 

Please advise.

Thanks,

Michael Combs

  • 0
    TI__Expert 6985 points
    Hello Michael!

    Where is the SDZ pin held during this cycling?

    7.3.3 Startup and Shutdown Operation
    The TPA31xxD2 family employs a shutdown mode of operation designed to reduce supply current (Icc) to the
    absolute minimum level during periods of nonuse for power conservation. The SDZ input terminal should be held
    high (see specification table for trip point) during normal operation when the amplifier is in use. Pulling SDZ low
    will put the outputs to mute and the amplifier to enter a low-current state. It is not recommended to leave SDZ
    unconnected, because amplifier operation would be unpredictable.

    Thanks, Jeff
  • 0
    TI__Mastermind 24835 points

    Hi Michael,

    Has your problem already been resolved? We never found the issue in MUTE function in TPA3118D2, it should be a system level issue. Could you confirm the constant high level on SD pin? If it is, could you please let me know whether the FAULT pin is connected to MUTE or SD? If FAULT pin is connected to MUTE or SD, you need to measure the waveform on FUALT, and confirm whether the FAULT occurs during the mute state. Please also show us your SCH for the further debug.

    Best regards,,

    Shawn Zheng

  • 0 in reply to Shawn Zheng
    Prodigy 20 points

    Shawn, yes the SD pin is always held high. SD and FAULT are tied together to a 100K to 12v. FAULT is not connected to MUTE. We have measured the outputs and it appears that the amp is toggling MUTE as we can see voltage at the outputs when unmuted. However, there is no audio about 50% of the time, which is why we suspected a MUTE problem. We have checked FAULT and there is NO FAULT when we see this problem.

  • 0 in reply to Michael Combs
    TI__Mastermind 24835 points

    Hi Michael,

    Basically, MUTE is input pin, it won't toggle the voltage automatically. Is it possible that MUTE toggling is caused by SDZ toggling? Did you measure the waveform on SDZ pin? How is MUTE pin connected? Is it connected to GND through a 100kOhm resistance? Any external controlling signal on it? Please show me your SCH, it would be helpful for further debug.

    Best regards,

    Shawn Zheng