WM8753L
Advanced Information
MBVSEL=0
MICBIAS
= 1.8 x VMID
= 0.9 X AVDD
VMID
MB
internal
resistor
MBVSEL=1
MICBIAS
= 1.5 x VMID
= 0.75 X AVDD
internal
resistor
AGND
Figure 8 Microphone Bias Schematic
MICBIAS CURRENT DETECT
The WM8753L includes a microphone bias current detect circuit which allows the user to set
thresholds for the microphone bias current, above which an interrupt will be triggered. There are two
separate interrupt bits, MICDET to allow the user to e.g. distinguish between one or two microphones
connected to the WM8753L, and MICSHT to detect a shorted microphone (mic button press). The
thresholds for the microphone bias current are set by MBTHRESH[2:0], for MICDET, and
MBSCTHRESH[1:0] for MICSHT. Thresholds for each code are shown in Table 15. The circuit is
enabled by setting MBCEN.
See the GPIO and Interrupt Controller sections for details on the interrupt and status readback for the
microphone bias current detect.
REGISTER
ADDRESS
BIT
LABEL
DEFAULT
DESCRIPTION
R51 (33h)
5:4
MBSCTHRESH
00
Microphone Bias, Shorted Current
Threshold Select
00: 500uA
01: 1000uA
10: 1600uA
11: 2300uA
These values are for 3.3V supply and
scale with supply voltage.
3:1
MBTHRESH
000
Microphone Bias, Current Threshold
Select
000:250uA
001:410uA
….160uA steps up to
111:1370uA
These values are for 3.3V supply and
scale with supply voltage.
0
MBCEN
0
Mic Bias Current Comparator Circuit
enable
0 : Comparator disabled
1 : Comparator enabled
Table 15 Mic Bias Current Comparator Circuit Control
AI Rev 3.1 June 2004
w
27
WOLFSON [ WOLFSON MICROELECTRONICS PLC ]
