WM9713 datasheet(44/111 Pages) WOLFSON

44 / 111 page

WM9713L

Preliminary Technical Data

PTD, March 2004, Rev 2.2

The microphone bias is driven to a dedicated MICBIAS pin 28 and is enabled by MPOP1EN in

22h.

When not in use the microphone bias can be powered down using the Powerdown register bit

MICBIAS (register 3Eh, bit 14).

ADDRESS

BIT

LABEL

DEFAULT

DESCRIPTION

MBOP2EN

0 (Off)

Microphone bias enable to GPIO8 (pin 12)

MBOP1EN

0 (Off)

Microphone bias enable to MICBIAS (pin 28)

22h

MBVOL

Microphone bias voltage control

0: 0.9 * AVDD

1: 0.75 * AVDD

Table 23 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 WM9713L 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 WM9713L, 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 24

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 the

microphone bias current detect & microphone short circuit detect.

WM9713 Datasheet(PDF) 44 Page - Wolfson Microelectronics plc