PCM2912 datasheet(22/32 Pages) TI

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Microphone Amplifier

Input PGA

Sidetone Programmable Attenuator

Output Programmable Attenuator

VCOM1 and VCCM2

Filter Pins

DAC

VCOM

10kW

20kW

FR/FL

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.

VCOM2 (pin 12) is provided for the center voltage of a headphone amplifier. VCOM1 (pin 11) is provided for the

center voltage of all other analog circuit. Each VCOM pin must be decoupled with an appropriate capacitor.

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

important to prevent the pop-noise, especially for the VCOM2 (pin 12). The equivalent resistance of VCOM2 is 500

Ω, and VCOM1 is 15 kΩ.

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

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PCM2912 Datasheet(PDF) 22 Page - Texas Instruments