WM9714L_06 WOLFSON [Wolfson Microelectronics plc], WM9714L_06 Datasheet - Page 39

• Manufacturer Part Number: WM9714L_06
• Description: AC 97 Audio CODEC
• Manufacturer: WOLFSON [Wolfson Microelectronics plc]

Pre-Production
w
Table 24 Microphone Bias Voltage Control
The internal MICBIAS circuitry is shown in Figure 14. Note that the maximum source current
capability for MICBIAS is 3mA. The external biasing resistors therefore must be large enough to limit
the MICBIAS current to 3mA.
Figure 14 Microphone Bias Schematic
MICBIAS CURRENT DETECT
The WM9714L includes a microphone bias current detect circuit with programmable thresholds for
the microphone bias current, above which an interrupt will be triggered. There are two separate
interrupt bits, MICDET to e.g. distinguish between one or two microphones connected to the
WM9714L, and MICSHT to detect a shorted microphone (mic button press). The microphone current
detect threshold is set by MCDTHR[2:0], for MICDET, and MCDSCTHR[1:0] for MICSHT.
Thresholds for each code are shown in Table 25
When not in use the microphone bias current detect circuit can be powered down using the
Powerdown register bit MCD (register 3Eh, bit 15).
See the GPIO and Interrupt Controller sections for details on the interrupt and status readback for
these MICBIAS current detection features.
Table 25 Microphone Current Detect Control
22h
22h
REGISTER
REGISTER
ADDRESS
ADDRESS
7
6
5
4:2
1:0
BIT
BIT
MBOP2EN
MBOP1EN
MBVOL
MCDTHR
MCDSCTR
LABEL
LABEL
0 (Off)
1 (On)
0
DEFAULT
000
00
DEFAULT
0: 0.9 * AVDD
1: 0.75 * AVDD
Microphone bias enable to GPIO8 (pin 12)
Microphone bias enable to MICBIAS (pin 28)
Microphone bias voltage control
Mic current detect threshold
000:100uA
001:200uA
….100uA steps up to
111:800uA
These values are for 3.3V supply and scale
with supply voltage (AVDD).
Mic current detect short circuit threshold
00: 600uA
01: 1200uA
10: 1800uA
11: 2400uA
These values are for 3.3V supply and scale
with supply voltage (AVDD).
DESCRIPTION
DESCRIPTION
PP Rev 3.0 June 2006
WM9714L
39