Production Data
WM8750L
As an example, the WM8750 can be set up to convert one differential and one single ended mono
signal by applying the differential signal to LINPUT1/RINPUT1 and the single ended signal to
RINPUT2. By setting LINSEL to L-R Differential (see Table 3), DS to LINPUT1 - RINPUT1 (see Table
5) and RINSEL to RINPUT2, each mono signal can then be routed to a separate ADC or Bypass
path.
The signal inputs are biased internally to the reference voltage VREF. Whenever the line inputs are
muted or the device placed into standby mode, the inputs are kept biased to VREF using special anti-
thump circuitry. This reduces any audible clicks that may otherwise be heard when changing inputs.
DC MEASUREMENT
For DC measurements (for example, battery voltage monitoring), the input signal at the LINPUT1
and/or RINPUT1 pins can be taken directly into the respective ADC, bypassing both PGA and
microphone boost. The ADC output then becomes unsigned relative to AVDD, instead of being a
signed (two’s complement) number relative to VREF. Setting L/RDCM will override L/RINSEL. The
input range for dc measurement is AGND to AVDD.
REGISTER
ADDRESS
BIT
LABEL
LINSEL
DEFAULT
DESCRIPTION
R32 (20h)
Left Channel Input Select
00 = LINPUT1
7:6
00
ADC Signal
Path Control
(Left)
01 = LINPUT2
10 = LINPUT3
11 = L-R Differential (either LINPUT1-
RINPUT1 or LINPUT2-RINPUT2,
selected by DS)
LMICBOOST
RINSEL
Left Channel Microphone Gain Boost
00 = Boost off (bypassed)
01 = 13dB boost
5:4
7:6
00
00
10 = 20dB boost
11 = 29dB boost
R33 (21h)
Right Channel Input Select
00 = RINPUT1
ADC Signal
Path Control
(Right)
01 = RINPUT2
10 = RINPUT3
11 = L-R Differential (either LINPUT1-
RINPUT1 or LINPUT2-RINPUT2,
selected by DS)
RMICBOOST
Right Channel Microphone Gain Boost
00 = Boost off (bypassed)
01 = 13dB boost
5:4
00
10 = 20dB boost
11 = 29dB boost
Table 3 Input Software Control
REGISTER
ADDRESS
BIT
LABEL
RDCM
DEFAULT
DESCRIPTION
R31 (1Fh)
ADC input Mode
Right Channel DC Measurement
0 = Normal Operation, PGA Enabled
1 = Measure DC level on RINPUT1
Left Channel DC Measurement
5
0
LDCM
4
0
0 = Normal Operation, PGA Enabled
1 = Measure DC level on LINPUT1
Table 4 DC Measurement Select
PD, Rev 4.4, August 2012
19
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WOLFSON [ WOLFSON MICROELECTRONICS PLC ]
