WM8750LSEFLSLASHR datasheet(21/62 Pages) WOLFSON

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Production Data

WM8750L

PD Rev 4.2 August 2005

PGA CONTROL

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

adjustable from +30dB to –17.25dB 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. Additionally, by controlling

the register bits LIVU and RIVU, the left and right gain settings can be simultaneously updated.

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 register R23 (17h).

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

registers are shown in Table 9. If zero crossing is enabled, it is necessary to enable zero cross

timeout to un-mute the input PGAs. This is because their outputs will not cross zero when muted.

Alternatively, zero cross can be disabled before sending the un-mute command.

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

R0 (00h)

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

R1 (01h)

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

R23 (17h)

Additional

Control (1)

TOEN

Timeout Enable

0 : Timeout Disabled

1 : Timeout Enabled

Table 9 Input PGA Software Control

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