WM8753LEBSLASHV datasheet(28/87 Pages) WOLFSON

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Advanced Information

WM8753L

AI Rev 3.1 June 2004

PGA CONTROL

The PGA matches the input signal level to the ADC input range. The PGA gain is logarithmically

adjustable from –17.25dB to +30dB in 0.75dB steps. Each PGA can be controlled either by the user

or by the ALC function (see Automatic Level Control). When ALC is enabled for one or both channels,

then writing to the corresponding PGA control register has no effect.

The gain is independently adjustable on both Right and Left Line Inputs. However, by setting the

LRINBOTH or RLINBOTH bits whilst programming the PGA gain, both channels are simultaneously

updated. This reduces the required number of software writes required. Setting the LZCEN and

RZCEN bits enables a zero-cross detector which ensures that PGA gain changes only occur when

the signal is at zero, eliminating any zipper noise. If zero cross is enabled a timeout is also available

to update the gain if a zero cross does not occur. This function may be enabled by setting TOEN in

The inputs can also be muted in the analogue domain under software control. The software control

registers are shown in Table 16

ADDRESS

BIT

LABEL

DEFAULT

DESCRIPTION

LIVU

Left Volume Update

0 = Store LINVOL in intermediate

latch (no gain change)

1 = Update left and right channel

gains

(left

LINVOL,

right

intermediate latch)

LINMUTE

Left Channel Input Analogue Mute

1 = Enable Mute

0 = Disable Mute

Note: LIVU must be set to un-mute.

LZCEN

Left Channel Zero Cross Detector

1 = Change gain on zero cross only

0 = Change gain immediately

R49 (31h)

Left Channel

PGA

5:0

LINVOL

[5:0]

010111

( 0dB )

Left Channel Input Volume Control

111111 = +30dB

111110 = +29.25dB

. . 0.75dB steps down to

000000 = -17.25dB

RIVU

Right Volume Update

0 = Store RINVOL in intermediate

latch (no gain change)

1 = Update left and right channel

gains

(right

RINVOL,

left

intermediate latch)

RINMUTE

Right Channel Input Analogue Mute

1 = Enable Mute

0 = Disable Mute

Note: RIVU must be set to un-mute.

RZCEN

Right Channel Zero Cross Detector

1 = Change gain on zero cross only

0 = Change gain immediately

R50 (32h)

Right Channel

PGA

5:0

RINVOL

[5:0]

010111

( 0dB )

Right Channel Input Volume Control

111111 = +30dB

111110 = +29.25dB

. . 0.75dB steps down to

000000 = -17.25dB

R18 (12h)

Additional

Control

TOEN

Timeout Enable

0 : Timeout Disabled

1 : Timeout Enabled

Table 16 Input PGA Software Control

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