WM8350 Datasheet, PDF (100/340 Pages) Wolfson Microelectronics plc – Wolfson AudioPlus™ Stereo CODEC with Power Management

WM8350
Production Data
13.12.2 MICROPHONE DETECTION
The WM8350 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 WM8350 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
BIT
LABEL
DEFAULT
DESCRIPTION
R8 (08h)
8 MIC_DET_ENA
0
Enable MIC detect:
Power Mgmt 1
0 = disabled
R74 (4Ah)
7 MIC_DET_ENA
0
1 = enabled
Mic Bias
Control
4:2 MCDTHR [2:0]
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
w
PD, February 2011, Rev 4.4
100