WM8352
Production Data
13.12.2 MICROPHONE DETECTION
The WM8352 can detect when a microphone has been plugged in, and/or when the microphone is
short-circuited. It detects these events by comparing the current drawn from the MICBIAS pin against
two thresholds. The thresholds for plug-in detection and short-circuit detection are programmable.
A MICBIAS current above the MCDTHR threshold level is used to indicate that a microphone is
plugged in, and is associated with the CODEC_MICD_EINT interrupt. If the bias current exceeds the
MCDSCTHR limit, this indicates a microphone short-circuit condition, and the WM8352 raises a
CODEC_MICSCD_EINT interrupt. See Section 13.12.7 for further details. Note that the MICBIAS
current thresholds are subject to a wide tolerance - up to +/-50% of the specified value.
Microphone detection requires the internal slow clock to be enabled - see Section 12.3.6.
ADDRESS
R8 (08h)
BIT
LABEL
DEFAULT
DESCRIPTION
Enable MIC detect:
8
MIC_DET_ENA
0
Power Mgmt 1
R74 (4Ah)
0 = disabled
1 = enabled
7
MIC_DET_ENA
MCDTHR [2:0]
0
Mic Bias
Control
4:2
000
Threshold for bias current detection
000 = 160μA
001 = 330μA
010 = 500μA
011 = 680μA
100 = 850μA
101 = 1000μA
110 = 1200μA
111 = 1400μA
These threshold currents scale
proportionally with AVDD. The values
given are for AVDD=3.3V.
1:0
MCDSCTHR
[1:0]
00
Threshold for microphone short-circuit
detection
00 = 400μA
01 = 900μA
10 = 1350μA
11 = 1800μA
These threshold currents scale
proportionally with AVDD. The values
given are for AVDD=3.3V.
Note: MIC_DET_ENA can be accessed through R8 or through R74. Reading from or writing to either
register location has the same effect.
Table 49 Controlling Microphone Bias Current Detection
PD, February 2011, Rev 4.4
100
w
WOLFSON [ WOLFSON MICROELECTRONICS PLC ]
