WM8731SEDSSLASHR datasheet(22/63 Pages) WOLFSON

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WM8731 / WM8731L

Production Data

PD Rev 4.3 August 2006

The gain between the line inputs and the ADC is logarithmically adjustable from +12dB to –34.5dB in

1.5dB steps under software control. The ADC Full Scale input is 1.0V rms at AVDD = 3.3 volts. Any

voltage greater than full scale will possibly overload the ADC and cause distortion. Note that the full

scale input tracks directly with AVDD. The gain is independently adjustable on both Right and Left

Line Inputs. However, by setting the INBOTH bit whilst programming the volume control, both

channels are simultaneously updated with the same value. Use of INBOTH reduces the required

number of software writes required. The line inputs to the ADC can be muted in the analogue domain

under software control. The software control registers are shown Table 3. Note that the Line Input

Mute only mutes the input to the ADC, this will still allow the Line Input signal to pass to the line

output in Bypass Mode.

ADDRESS

BIT

LABEL

DEFAULT

DESCRIPTION

4:0

LINVOL[4:0]

10111

( 0dB )

Left Channel Line Input Volume

Control

11111 = +12dB . . 1.5dB steps down

to 00000 = -34.5dB

LINMUTE

Left Channel Line Input Mute to ADC

1 = Enable Mute

0 = Disable Mute

0000000

Left Line In

LRINBOTH

Left to Right Channel Line Input

Volume and Mute Data Load Control

1 = Enable Simultaneous Load of

LINVOL[4:0] and LINMUTE to

RINVOL[4:0] and RINMUTE

0 = Disable Simultaneous Load

4:0

RINVOL[4:0]

10111

( 0dB )

Right Channel Line Input Volume

Control

11111 = +12dB . .1.5dB steps down

to 00000 = -34.5dB

RINMUTE

Right Channel Line Input Mute to

ADC

1 = Enable Mute

0 = Disable Mute

0000001

Right Line In

RLINBOTH

Right to Left Channel Line Input

Volume and Mute Data Load Control

1 = Enable Simultaneous Load of

RINVOL[4:0] and RINMUTE to

LINVOL[4:0] and LINMUTE

0 = Disable Simultaneous Load

Table 3 Line Input Software Control

The line inputs are biased internally through the operational amplifier to VMID. Whenever the line

inputs are muted or the device placed into standby mode, the line inputs are kept biased to VMID

using special anti-thump circuitry. This reduces any audible clicks that may otherwise be heard when

re-activating the inputs.

The external components required to complete the line input application is shown in the Figure 11.

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