WM9712CLGEFLSLASHV datasheet(17/78 Pages) WOLFSON

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Production Data

WM9712L

PD, Rev 4.6, November 2011

AGND

MICBIAS

= 1.8 x CAP2

= 0.9 X AVDD

CAP2

WM9712L

Figure 2 Microphone Bias Schematic

PHONE INPUT

Pin 20 (PHONE) is a mono, line level input designed to connect to the receive path of a telephony

device.

The pin connects directly to the record selector for phone call recording (Note: to record both sides of

a phone call, one ADC channel should record the PHONE signal while the other channel records the

MIC signal). The RECVOL PGA adjusts the recording volume, controlled by register 1Ch or by the

ALC function.

To listen to the PHONE signal, the signal passes through a separate PGA, controlled by register 0Ch.

The signal can be routed into the headphone mixer (for normal phone call operation) and/or the

speaker mixer (for speakerphone operation), but not into the phone mixer (to prevent forming a

feedback loop). When the phone input is not used, the phone-in PGA can be switched off to save

power (see “Power Management” section).

PHONE is biased internally to the reference voltage VREF. Whenever the input is muted or the

device placed into standby mode, the input remains biased to VREF using special anti-thump circuitry

to suppress any audible clicks when changing inputs.

ADDRESS

BIT

LABEL

DEFAULT

DESCRIPTION

0Ch

Phone Input

P2H

Mute PHONE path to headphone mixer

1: Mute, 0: No mute (ON)

P2S

Mute PHONE path to speaker mixer

1: Mute, 0: No mute (ON)

4:0

PHONE

VOL

01000

(0dB)

PHONE input gain

00000: +12dB

… (1.5dB steps)

11111: -34.5dB

Table 4 Phone Input Control

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