WM9715L
Production Data
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).
REGISTER
ADDRESS
BIT
14
LABEL
M12P
DEFAULT
DESCRIPTION
0Eh
1
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
Mic Volume
13
M22P
1
12:8
LMICVOL
01000
(0dB)
7
20dB
MS
0
Microphone gain boost (Note 1)
1: 20dB boost ON
0: No boost (0dB gain)
6:5
00
Microphone mode select
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
4:0
8
MICVOL
DS
01000
(0dB)
Microphone volume to mixers
00000: +12dB
… (1.5dB steps)
11111: -34.5dB
5Ch
0
Differential Microphone Select
0 : Use MIC1 and MIC2
1: Use LINEL and LINER (Note 2)
Additional
Analogue
Functions
Table 3 Microphone Input Control
Note:
1. 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.
2. 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.
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.
PD Rev 4.0 December 2007
16
w
WOLFSON [ WOLFSON MICROELECTRONICS PLC ]
