WM8994ECSSLASHR datasheet(124/363 Pages) CIRRUS

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WM8994

124

Rev 4.6

OUTPUT SIGNAL PATH VOLUME CONTROL

There are six output PGAs - MIXOUTLVOL, MIXOUTRVOL, HPOUT1LVOL, HPOUT1RVOL,

SPKLVOL and SPKRVOL. Each can be independently controlled, with MIXOUTLVOL and

MIXOUTRVOL providing volume control to both the earpiece and line drivers, HPOUT1LVOL and

HPOUT1RVOL to the headphone driver, and SPKLVOL and SPKRVOL to the speaker drivers.

The volume control of each of these output PGAs can be adjusted over a wide range of values. To

minimise pop noise, it is recommended that only the MIXOUTLVOL, MIXOUTRVOL, HPOUT1LVOL,

HPOUT1RVOL, SPKLVOL and SPKRVOL are modified while the output signal path is active. Other

gain controls are provided in the signal paths to provide scaling of signals from different sources, and

to prevent clipping when multiple signals are mixed. However, to prevent pop noise, it is

recommended that those other gain controls should not be modified while the signal path is active.

To prevent "zipper noise", a zero-cross function is provided on the 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.

The mixer output PGA controls are shown in Table 62. The MIXOUT_VU bits control the loading of the

output mixer PGA volume data. When MIXOUT_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 output mixer PGA

volume settings are both updated when a 1 is written to either MIXOUT_VU bit. This makes it possible

to update the gain of both output paths simultaneously.

ADDRESS

BIT

LABEL

DEFAULT

DESCRIPTION

R32 (0020h)

Left OPGA

Volume

MIXOUT_VU

N/A

Mixer Output PGA Volume Update

Writing a 1 to this bit will update

MIXOUTLVOL and MIXOUTRVOL

volumes simultaneously.

MIXOUTL_ZC

MIXOUTLVOL (Left Mixer Output

PGA) Zero Cross Enable

0 = Zero cross disabled

1 = Zero cross enabled

MIXOUTL_MUTE_N

MIXOUTLVOL (Left Mixer Output

PGA) Mute

0 = Mute

1 = Un-mute

5:0

MIXOUTL_VOL [5:0]

39h

(0dB)

MIXOUTLVOL (Left Mixer Output

PGA) Volume

-57dB to +6dB in 1dB steps

00_0000 = -57dB

00_0001 = -56dB

… (1dB steps)

11_1111 = +6dB

(See Table 65 for output PGA

volume control range)

R33 (0021h)

Right OPGA

Volume

MIXOUT_VU

N/A

Mixer Output PGA Volume Update

Writing a 1 to this bit will update

MIXOUTLVOL and MIXOUTRVOL

volumes simultaneously.

MIXOUTR_ZC

MIXOUTRVOL (Right Mixer Output

PGA) Zero Cross Enable

0 = Zero cross disabled

1 = Zero cross enabled

MIXOUTR_MUTE_N

MIXOUTLVOL (Right Mixer Output

PGA) Mute

0 = Mute

1 = Un-mute

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