wm9712l Wolfson Microelectronics plc, wm9712l Datasheet - Page 16

• Manufacturer Part Number: wm9712l
• Description: Ac?97 Audio And Touchpanel Codec
• Manufacturer: Wolfson Microelectronics plc

WM9712L
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It is also possible to use the LINEINL and LINEINR pins as a second differential microphone input.
This is achieved by setting the DS bit (register 5Ch, bit 11) to ‘1’. This disables the line-in audio paths
and routes the signal from LINEINL and LINEINR through the differential mic path, as if it came from
the MIC1 and MIC2 pins. Only one differential microphone be used at a time. The DS bit only has an
effect when MS = 01 (differential mode).
Table 3 Microphone Input Control
Note:
1.
2.
MICROPHONE BIAS
The MICBIAS output (pin 28) provides a low noise reference voltage suitable for biasing electret type
microphones and the associated external resistor biasing network. The internal MICBIAS circuitry is
shown below. Note that the maximum source current capability for MICBIAS is 3mA. The external
biasing resistors and microphone cartridge therefore must limit the MICBIAS current to 3mA.
0Eh
Mic Volume
5Ch
Additional
Analogue
Functions
REGISTER
ADDRESS
The 20dB gain boost acts on the input to the phone mixer only. A separate microphone
boost for recording can be enabled using the BOOST bit in register 1Ah.
When the LINEL and LINER are selected for differential microphone select then the
MIC1 and MIC2 input pins become disabled, these signals can therefore not be routed
internally to the device.
14
13
12:8
7
6:5
4:0
8
BIT
M12P
M22P
LMICVOL
20dB
MS
MICVOL
DS
LABEL
1
1
01000
(0dB)
0
00
01000
(0dB)
0
DEFAULT
Mute MIC1 path to phone mixer
1: Mute, 0: No mute (ON)
Mute MIC2 path to phone mixer
1: Mute, 0: No mute (ON)
Left microphone volume
Only used when MS = 11
Similar to MICVOL
Microphone gain boost (Note 1)
1: 20dB boost ON
0: No boost (0dB gain)
Microphone mode select
Microphone volume to mixers
00000: +12dB
… (1.5dB steps)
11111: -34.5dB
Differential Microphone Select
0 : Use MIC1 and MIC2
1: Use LINEL and LINER (Note 2)
00
01
10
11
Single-ended mono (left)
left = right = MIC1 (pin 21)
Volume controlled by MICVOL
Differential mono mode
left = right = MIC1 – MIC2
Volume controlled by MICVOL
Single-ended mono (right)
left = right = MIC2 (pin 22)
Volume controlled by MICVOL
Stereo mode
MIC1 = left, MIC2 = right
Left Volume controlled by LMICVOL
Right volume controlled by MICVOL
DESCRIPTION
PD Rev 4.5 August 2006
Production Data
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