WM8959 Wolfson Microelectronics Ltd., WM8959 Datasheet - Page 39

• Manufacturer Part Number: WM8959
• Description: Mobile Multimedia DAC with Dual-mode Class AB/D Speaker Driver
• Manufacturer: Wolfson Microelectronics Ltd.

w
Pre-Production
MICROPHONE BIAS CONTROL
The MICBIAS output provides a low noise reference voltage suitable for biasing electret type
microphones via an external resistor. Refer to the Applications Information section for recommended
external components. The MICBIAS voltage can be enabled or disabled using the MICBIAS_ENA
control bit and the voltage can be selected using the MBSEL register bit as detailed in Table 3.
Table 3 Microphone Bias Control
Note that the maximum source current capability for MICBIAS is 3mA. The external biasing
resistance must be large enough to limit the MICBIAS current to 3mA.
MICROPHONE CURRENT DETECT
A MICBIAS current detect function allows detection of accessories such as headset microphones.
When the MICBIAS load current exceeds one of two programmable thresholds, (e.g. short circuit
current or normal operating current), an interrupt or GPIO output can be generated. The current
detection circuit is enabled by the MCD bit; the current thresholds are selected by the MCDTHR and
MCDSCTH register fields as described in Table 41 - see “General Purpose Input/Output” for a full
description of these fields.
REGISTER
ADDRESS
R1 (01h)
R58 (3Ah)
4
0
BIT
MICBIAS_ENA
(rw)
MBSEL
LABEL
DEFAULT
0b
0b
Microphone Bias
0 = OFF (high impedance output)
1 = ON
Microphone Bias Voltage Control
0 = 0.9 * AVDD
1 = 0.65 * AVDD
DESCRIPTION
PP, May 2008, Rev 3.1
WM8959
39