WM8776 datasheet(28/55 Pages) WOLFSON

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WM8776

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PP Rev 1.91 June 2004

ANALOGUE OUTPUT VOLUME CONTROLS

There are analogue volume controls for the headphone outputs which may be adjusted

independently using separate volume control registers.

ADDRESS

BIT

LABEL

DEFAULT

DESCRIPTION

6:0

HPLA[6:0]

1111001

(0dB)

Attenuation data for Headphone Left channel in 1dB steps. See

Table 13

HPLZCEN

Headphone left zero cross detect enable

0: zero cross disabled

1: zero cross enabled

R0 (00h)

0000000

Analogue

Attenuation

Headphone

Output Left

UPDATE

Not latched

Controls simultaneous update of Headphone Attenuation Latches

0: Store HPLA in intermediate latch (no change to output)

1: Store HPLA and update attenuation on both channels.

6:0

HPLA[6:0]

1111001

(0dB)

Attenuation data for Headphone Right channel in 1dB steps. See

Table 13

HPRZCEN

Headphone right zero cross detect enable

0: zero cross disabled

1: zero cross enabled

R1 (01h)

0000001

Analogue

Attenuation

Headphone

Output Right

UPDATE

Not latched

Controls simultaneous update of Headphone Attenuation Latches

0: Store HPRA in intermediate latch (no change to output)

1: Store HPRA and update attenuation on both channels.

6:0

HPMASTA

[6:0]

1111001

(0dB)

Attenuation data for both Headphone channels in 1dB steps. See

Table 13

MZCEN

Master zero cross detect enable

0: zero cross disabled

1: zero cross enabled

R2 (02h)

0000010

Headphone

Master

Analogue

Attenuation

(both channels)

UPDATEA

Not latched

Controls simultaneous update of Attenuation Latches

0: Store gain in intermediate latch (no change to output)

1: Store gain and update attenuation on all channels.

R13 (0Dh)

0001101

Power Down

HPPD

Headphone output/PGA Power Down

0 : HP out enabled

1 : HP out disabled

Table 12 Headphone Attenuation Register Map

Each analogue headphone output channel has a PGA which can be used to attenuate the

output from that channel. The PGA’s can be powered up or down using the HPPD bit.

Attenuation is 0dB by default but can be set between +6dB and –73dB in 1dB steps using the

two Attenuation control words. The attenuation registers are double latched allowing them to

be updated in pairs. Setting the UPDATE bit on an attenuation write to one channel, for

example HPOUTL, will cause the pre-latched value in HPOUTR to be applied to the PGA. A

master attenuation register is also included, allowing both volume levels to be set to the

same value in a single write.

Note: The UPDATE bit is not latched. If UPDATE=0, the Attenuation value will be written to

the pre-latch but not applied to the PGA. If UPDATE=1, pre-latched values will be applied

from the next input sample. Writing to HPMASTA[6:0] overwrites any values previously sent

to HPLA[6:0] and HPRA[6:0].

HEADPHONE OUTPUT PGA ATTENUATION

The analogue output PGAs are controlled by the HPLA and HPRA registers. Register bits

MASTA can be used to control attenuation of both channels.

Table 13 shows how the attenuation levels are selected from the 7-bit words.

WM8776 Datasheet(PDF) 28 Page - Wolfson Microelectronics plc

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