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Microphone Amplifier

Input PGA

Sidetone Programmable Attenuator

Output Programmable Attenuator

Filter Pins

DAC

VCOM

10kW

20kW

FR/FL

Cf

SideTone

–

+

20kW

10kW

PCM2912

SLES216 – FEBRUARY 2008

The PCM2912 has the low-noise, single-ended mono microphone amplifier with mute function which is controlled

by MUTE (pin 30). The signal gain is selectable by MAMP (pin 23). The noise level at input node is 5

µVrms, and

the input impedance is 20 k

Ω.

The PCM2912 has the low-noise input programmable gain amplifier (PGA) for the microphone amplifier

output/ADC input, whose gain range is +30 dB to –12 dB in 1dB/step.

The PCM2912 has the low-noise, sidetone programmable attenuator with mute function for the sidetone signal

path (microphone amplifier output to output PGA input), whose gain range is 0 dB to –76 dB in 1 dB/step.

The PCM2912 has the low-noise output programmable attenuator with mute function for mixed signal, which

affects DAC output signal and sidetone signal. The output PGA gain range is 0 dB to –76 dB in 1 dB/step.

Because the headphone output is disconnected when entering the suspend state, determining the capacitance is

k

FL (pin 9) and FR (pin 10) are provided to make an LPF to decrease the DAC outband noise.

This is optional.

Figure 32. Filter Circuit

22

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