WM8940 datasheet(46/85 Pages) WOLFSON

46 / 85 page

WM8940

Pre-Production

Pre-Production, Rev 3.0, February 2007

ADDRESS

BIT

LABEL

DEFAULT

DESCRIPTION

MONOATTN

Attenuation control for bypass path

(output of input boost stage) to mono

mixer input

0 = 0dB

1 = -10dB

MONOMUTE

0=No mute

1=Output muted. During mute the

mono output will output VMID which can

be used as a DC reference for a

headphone out.

AUX2MONO

Output of Auxilary amplifier to mono

mixer input:

0 = not selected

1 = selected

BYP2MONO

Bypass path (output of input boost

stage) to mono mixer input

0 = non selected

1 = selected

R56

Mono mixer

control

DAC2MONO

Output of DAC to mono mixer input

0 = not selected

1 = selected

Table 37 Mono Mixer Control

ENABLING THE OUTPUTS

Each analogue output of the WM8940 can be separately enabled or disabled. The analogue mixer

associated with each output has a separate enable. All outputs are disabled by default. To save

power, unused parts of the WM8940 should remain disabled.

Outputs can be enabled at any time, but it is not recommended to do so when BUFIO is disabled

(BUFIOEN=0), as this may cause pop noise (see “POP Minimisation” section).

ADDRESS

BIT

LABEL

DEFAULT

DESCRIPTION

BIASEN

Analogue amplifiers bias enable

Power

management 1

BUFIOEN

VMID buffer enable

MONOEN

MONOOUT enable

SPKNEN

SPKOUTN enable

SPKPEN

SPKOUTP enable

MONOMIXEN 0

Mono mixer enable

Power

management 3

SPKMIXEN

Speaker Mixer enable

Note:

All “Enable” bits are 1 = ON, 0 = OFF

Table 38 Output Stages Power Management Control

UNUSED ANALOGUE INPUTS/OUTPUTS

Whenever an analogue input/output is disabled, it remains connected to AVDD/2 through a resistor.

This helps to prevent pop noise when the output is re-enabled. The resistance between the voltage

buffer and the output pins can be controlled using the VROI control bit. The default impedance is

low, so that any capacitors on the outputs can charge up quickly at start-up. If a high impedance is

desired for disabled outputs, VROI can then be set to 1, increasing the resistance to about 30k

Ω.

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