WM8739 / WM8739L

Advanced Information

AI Rev 2.2 September 2001

12

12.5K

VMID

LINEIN

To

ADC

Figure 8 Line Input Schematic

LINE INPUT SCHEMATIC

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. Use of INBOTH reduces the required number of software

writes required. The line inputs can be muted in the analogue domain under software control. The

software control registers are shown below.

REGISTER

ADDRESS

BIT

LABEL

DEFAULT

DESCRIPTION

4:0

LINVOL[0:4]

10111

( 0dB )

Left Channel Line Input Volume Control

11111 = +12dB

. . 1.5dB steps down to

00000 = -34.5dB

7

LINMUTE

1

Left Channel Line Input Mute

1 = Enable Mute

0 = Disable Mute

0000000

Left Line In

8

LRINBOTH

0

Left to Right Channel Line Input Volume

and Mute Data Load Control

1 = Enable Simultaneous Load of

LINVOL[0:4] and LINMUTE to

RINVOL[0:4] and RINMUTE

0 = Disable Simultaneous Load

4:0

RINVOL[0:4]

10111

( 0dB )

Right Channel Line Input Volume Control

11111 = +12dB

. . 1.5dB steps down to

00000 = -34.5dB

7

RINMUTE

1

Left Channel Line Input Mute

1 = Enable Mute

0 = Disable Mute

0000001

Right Line In

8

RLINBOTH

0

Right to Left Channel Line Input Volume

and Mute Data Load Control

1 = Enable Simultaneous Load of

RINVOL[0:4] and RINMUTE to

LINVOL[0:4] and LINMUTE

0 = Disable Simultaneous Load

Table 2 Line Input Software Control