WM8753 Wolfson Microelectronics plc, WM8753 Datasheet - Page 27

• Manufacturer Part Number: WM8753
• Description: HI FI AND TELEPHONY DUAL CODEC
• Manufacturer: Wolfson Microelectronics plc

WM8753L
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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.
Table 15 Mic Bias Current Comparator Circuit Control
R51 (33h)
REGISTER
ADDRESS
VMID
5:4
3:1
0
BIT
MBSCTHRESH
MBTHRESH
MBCEN
LABEL
internal
resistor
internal
resistor
00
000
0
DEFAULT
AGND
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.
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.
Mic Bias Current Comparator Circuit
enable
0 : Comparator disabled
1 : Comparator enabled
MB
DESCRIPTION
MBVSEL=0
MICBIAS
= 1.8 x VMID
= 0.9 X AVDD
MBVSEL=1
MICBIAS
= 1.5 x VMID
= 0.75 X AVDD
AI Rev 3.1 June 2004
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