Electronic – Analog Mute Circuit – Simplest Solution

analogaudio

I'm building a simple analog mute circuit and I need advice on the simplest way to achieve my goal.

I have a GPIO pin that goes high when audio is playing and low when it's not. When audio is not playing, I need to connect AGND to the L & R channels of the audio circuit.

Obviously, I could do this with a transistor if the GPIO pin were reversed, but it's not. Is there an Active-Low component that I can use to achieve this goal? Preferably something in a small form factor.

EDIT: The audio circuit is driven by a PCM5102A DAC. It's a 2.1v RMS single-ended line driver that is ground centered. I do not believe there is DC Bias.

Best Answer

The PCM5102A datasheet suggests that this can be done on the chip itself.

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XSMT, pin 17, input, Soft mute control: Soft mute (Low) / soft un-mute (High).

From the datasheet:

11.2 Recommended Powerdown Sequence

Under certain conditions, the PCM510xA devices can exhibit some pop on power down. Pops are caused by a device not having enough time to detect power loss and start the muting process.

The PCM510xA devices have two auto-mute functions to mute the device upon power loss (intentional or unintentional).

XSMT = 0

When the XSMT pin is pulled low, the incoming PCM data is attenuated to 0, closely followed by a hard analog mute. This process takes 150 sample times (ts ) + 0.2 ms. Because this mute time is mainly dominated by the sampling frequency, systems sampling at 192 kHz will mute much faster than a 48-kHz system.

Clock Error Detect

When clock error is detected on the incoming data clock, the PCM510xA devices switch to an internal oscillator, and continue to the drive the output, while attenuating the data from the last known value. Once this process is complete, the PCM510xA outputs are hard muted to ground.

I don't think you'll have any noise.

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