WM8955BL Wolfson Microelectronics, WM8955BL Datasheet - Page 20

• Manufacturer Part Number: WM8955BL
• Description: Stereo DAC
• Manufacturer: Wolfson Microelectronics

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WM8955BL
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].
Table 7 Left Output Mixer Control
R34 (22h)
Left Mixer (1)
R35 (23h)
Left Mixer (2)
REGISTER
ADDRESS
8
7
6:4
8
7
6:4
BIT
LD2LO
LI2LO
LI2LOVOL
RD2LO
MI2LO
MI2LOVOL
LABEL
0
0
101
(-9dB)
0
0
101
(-9dB)
DEFAULT
Left DAC to Left Mixer
0 = Disable (Mute)
1 = Enable Path
LINEINL Signal to Left Mixer
0 = Disable (Mute)
1 = Enable Path
LINEINL Signal to Left Mixer Volume
000 = +6dB
… (3dB steps)
111 = -15dB
Right DAC to Left Mixer
0 = Disable (Mute)
1 = Enable Path
MONOIN Signal to Left Mixer
0 = Disable (Mute)
1 = Enable Path
MONOIN Signal to Left Mixer Volume
000 = +6dB
… (3dB steps)
111 = -15dB
DESCRIPTION
PD Rev 4.1 February 2007
Production Data
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