WM8959 datasheet(39/155 Pages) WOLFSON

39 / 155 page

Pre-Production

WM8959

PP, May 2008, Rev 3.1

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.

ADDRESS

BIT

LABEL

DEFAULT

DESCRIPTION

R1 (01h)

MICBIAS_ENA

(rw)

Microphone Bias

0 = OFF (high impedance output)

1 = ON

R58 (3Ah)

MBSEL

Microphone Bias Voltage Control

0 = 0.9 * AVDD

1 = 0.65 * AVDD

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.

WM8959 データシート(PDF) 39 Page - Wolfson Microelectronics plc