WM8955BLGECOSLASHV datasheet(20/44 Pages) WOLFSON

20 / 44 page

WM8955BL

Production Data

PD Rev 4.1 February 2007

LINE INPUTS AND OUTPUT MIXERS

The WM8955BL provides the option to mix the DAC output signal with analogue line-in signals from

the LINEINL, LINEINR and MONOIN+ and MONOIN- pins. The level of the mixed-in signals can be

controlled with PGAs (Programmable Gain Amplifiers).

LINEINL, LINEINR, MONOIN+ and MONOIN- are high impedance, low capacitance AC coupled

analogue inputs. They are biased internally to the reference voltage VREF. Whenever these inputs

are muted or the device placed into standby mode, the inputs remain biased to VREF using special

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

the inputs.

The mono mixer is designed to allow a number of signal combinations to be mixed, including the

possibility of mixing both the right and left channels together to produce a mono output. To prevent

overloading of the mixer when full-scale DAC left and right signals are input, the mixer inputs from the

DAC outputs each have a fixed gain of -6dB. The bypass path inputs to the mono mixer have variable

gain as determined by R38/R39 bits [6:4].

ADDRESS

BIT

LABEL

DEFAULT

DESCRIPTION

LD2LO

Left DAC to Left Mixer

0 = Disable (Mute)

1 = Enable Path

LI2LO

LINEINL Signal to Left Mixer

0 = Disable (Mute)

1 = Enable Path

R34 (22h)

Left Mixer (1)

6:4

LI2LOVOL

101

(-9dB)

LINEINL Signal to Left Mixer Volume

000 = +6dB

… (3dB steps)

111 = -15dB

RD2LO

Right DAC to Left Mixer

0 = Disable (Mute)

1 = Enable Path

MI2LO

MONOIN Signal to Left Mixer

0 = Disable (Mute)

1 = Enable Path

R35 (23h)

Left Mixer (2)

6:4

MI2LOVOL

101

(-9dB)

MONOIN Signal to Left Mixer Volume

000 = +6dB

… (3dB steps)

111 = -15dB

Table 7 Left Output Mixer Control

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