WM8962B datasheet(129/295 Pages) WOLFSON

129 / 295 page

WM8962

Rev 4.3

129

HEADPHONE OUTPUT PGA CONTROL

There are four headphone output PGAs

– two primary (HPOUTL and HPOUTR), and two secondary

(HP1L, HP1R). The headphone outputs are each controlled by a primary PGA and a secondary PGA

in series.

The HPOUTL and HPOUTR PGAs give a high degree of control from -68dB to +6dB in 1dB steps. A

detailed table of all HPOUTL and HPOUTR gain settings is shown in Table 73. Secondary PGAs for

HPOUTL and HPOUTR provide control from -7dB to 0dB in 1dB steps on each channel. See Figure

33 for a representation of this layout.

The HPOUT PGAs are controlled using the HPOUTL_VOL and HPOUTR_VOL registers, providing

fine volume control to HPOUTL and HPOUTR.

To prevent "zipper noise", a zero-cross function is provided on the HPOUTL and HPOUTR output

PGAs. When this feature is enabled, volume updates will not take place until a zero-crossing is

detected. In the case of a long period without zero-crossings, a timeout function is provided. When the

zero-cross function is enabled, the volume will update after the timeout period if no earlier zero-cross

has occurred. The timeout clock is enabled using TOCLK_ENA; the timeout period is set by

TOCLK_DIV

. See “Clocking and Sample Rates” for more information on these fields.

It is recommended that only HPOUTL PGA and HPOUTR PGA are modified while the output signal

path is active as these are the only Headphone PGAs with the zero-cross function. It is recommended

that the other gain controls on the signal paths should not be modified while the signal path is active.

The left and right channels can also be attenuated independently using the HP1L_VOL and

HP1R_VOL registers. Note that there is no zero-cross function associated with these registers.

The

headphone

output

signal

can

muted

using

the

HPOUTL_PGA_MUTE

and

HPOUTR_PGA_MUTE registers. The headphone outputs are un-muted by default.

The HPOUT_VU bits control the loading of the Headphone Output PGA volume data and the PGA

mute functions. When HPOUT_VU is set to 0, the volume control data will be loaded into the

respective control register, but will not actually change the gain setting. The left and right Headphone

Output PGA volume settings are both updated when a 1 is written to any of the HPOUT_VU bits.

Similarly, the HPOUTL_PGA_MUTE and HPOUTR_PGA_MUTE settings are only effective when a 1

is written to either HPOUT_VU bit. This makes it possible to update the gain of the left and right output

paths simultaneously.

Note that the HP1L_VOL and HP1R_VOL registers are effective immediately when updated; the

HPOUT_VU bits have no control over the Secondary PGA volume registers. For best performance,

the Secondary PGA volume registers should be set to 000b (-

7dB). See “Reference Voltages and

Bias Control

” for further details of the High Performance headphone playback configuration.

ADDRESS

BIT

LABEL

DEFAULT

DESCRIPTION

R2 (2h)

HPOUTL

volume

HPOUT_VU

N/A

Headphone Output PGA Volume and

Mute Update.

Writing 1 to this bit will cause the

HPOUTL and HPOUTR volume and

mute settings to be updated

simultaneously.

HPOUTL_ZC

Left Headphone Output PGA Zero

Cross Enable

0 = Zero cross disabled

1 = Zero cross enabled

6:0

HPOUTL_VOL [6:0]

(Mute)

Left Headphone Output PGA Volume

000_0000 to 010_1111 = Mute

011_0000 to 011_0101 = -68dB

011_0110 = -67dB

…in 1dB steps

111_1001 = 0dB

…

111_1111 = +6dB

(See Table 73 for full volume control

range)

WM8962B Datasheet(PDF) 129 Page - Wolfson Microelectronics plc

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