wm8987 Wolfson Microelectronics plc, wm8987 Datasheet - Page 18

• Manufacturer Part Number: wm8987
• Description: Stereo Codec For Portable Audio Applications
• Manufacturer: Wolfson Microelectronics plc

WM8987L
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As an example, the WM8987L 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 4), DS to LINPUT1 - RINPUT1 and
RINSEL to RINPUT2, each mono signal can then be routed to a separate ADC or Bypass pat
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.
Table 4 Input Software Control
Table 5 DC Measurement Select
R32 (20h)
ADC Signal
Path Control
(Left)
R33 (21h)
ADC Signal
Path Control
(Right)
R31 (1Fh)
ADC input Mode
REGISTER
REGISTER
ADDRESS
ADDRESS
7:6
5:4
7:6
5:4
BIT
BIT
5
4
LINSEL
LMICBOOST
RINSEL
RMICBOOST
RDCM
LDCM
LABEL
LABEL
00
00
00
00
0
0
DEFAULT
DEFAULT
Left Channel Input Select
00 = LINPUT1
01 = LINPUT2
10 = Reserved
11 = L-R Differential (either LINPUT1-
Left Channel Microphone Gain Boost
00 = Boost off (bypassed)
01 = 13dB boost
10 = 20dB boost
11 = 29dB boost
Right Channel Input Select
00 = RINPUT1
01 = RINPUT2
10 = Reserved
11 = L-R Differential (either LINPUT1-
00 = Boost off (bypassed)
01 = 13dB boost
10 = 20dB boost
11 = 29dB boost
Right Channel DC Measurement
0 = Normal Operation, PGA Enabled
1 = Measure DC level on RINPUT1
Left Channel DC Measurement
0 = Normal Operation, PGA Enabled
1 = Measure DC level on LINPUT1
Right Channel Microphone Gain Boost
RINPUT1 or LINPUT2-RINPUT2,
selected by DS)
RINPUT1 or LINPUT2-RINPUT2,
selected by DS)
DESCRIPTION
DESCRIPTION
PD Rev 4.0 August 2008
Production Data
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