WM8945ECSSLASHR datasheet(24/169 Pages) WOLFSON

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WM8945

Production Data

PD, May 2011, Rev 4.1

INPUT PGA ENABLE

The input PGA (Programmable Gain Amplifiers) is enabled using the register bit INPPGAL_ENA, as

described in Table 1.

ADDRESS

BIT

LABEL

DEFAULT

DESCRIPTION

R2 (02h)

Power

Management 1

INPPGAL_ENA

Left Input PGA Enable

0 = Disabled

1 = Enabled

Table 1 Input PGA Enable

To enable the input PGA, the reference voltage VMID and the bias current must also be enabled. See

“Reference Voltages and Master Bias” for details of the associated controls VMID_SEL and

BIAS_ENA.

INPUT PGA CONFIGURATION

Microphone and Line level audio inputs can be connected to the WM8945 in single-ended or

differential configurations. (These two configurations are illustrated in Figure 61 and Figure 62 in the

section describing the external components requirements – see “Applications Information”.)

For single-ended microphone inputs, the microphone signal is connected to the non-inverting input of

the PGA, whilst the inverting input of the PGA is connected to VMID. For differential microphone

inputs, the non-inverted microphone signal is connected to the non-inverting input of the PGA, whilst

the inverted (or ‘noisy ground’) signal is connected to the inverting input pin.

Line level inputs are connected in the same way as a single-ended microphone signal.

The non-inverting input of the PGA is configured using the P_PGAL_SEL register. This register allows

the selection of three possible input pins to the PGA. When the AUX1 or AUX2 pin is used as an

audio input, that pin must be configured for audio using the AUX1_AUDIO or AUX2_AUDIO register

bits.

The inverting input of the PGA is configured using MICLN_TO_N_PGAL. This register allows the PGA

to operate in either single-ended or pseudo-differential configuration.

The registers for configuring the Input PGA are described in Table 2.

ADDRESS

BIT

LABEL

DEFAULT

DESCRIPTION

R39 (27h)

Input Ctrl

AUX2_AUDIO

AUX2 pin configuration

0 = Non-Audio signal

1 = AC-coupled Audio signal

AUX1_AUDIO

AUX1 pin configuration

0 = Non-Audio signal

1 = AC-coupled Audio signal

MICLN_TO_N_

PGAL

Left Input PGA Inverting Input

Select

0 = Connected to VMID

1 = Connected to IN2L

1:0

P_PGAL_SEL

[1:0]

Left Input PGA Non-Inverting Input

Select

00 = Connected to IN2L

01 = Connected to IN1L

10 = Connected to AUX1

11 = Reserved

Table 2 Input PGA Configuration

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