WM9714LGEFLSLASHV datasheet(39/94 Pages) WOLFSON

39 / 94 page

Pre-Production

WM9714L

PP Rev 3.0 June 2006

ADDRESS

BIT

LABEL

DEFAULT

DESCRIPTION

MBOP2EN

0 (Off)

Microphone bias enable to GPIO8 (pin 12)

MBOP1EN

1 (On)

Microphone bias enable to MICBIAS (pin 28)

22h

MBVOL

Microphone bias voltage control

0: 0.9 * AVDD

1: 0.75 * AVDD

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.

ADDRESS

BIT

LABEL

DEFAULT

DESCRIPTION

4:2

MCDTHR

000

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).

22h

1:0

MCDSCTR

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).

Table 25 Microphone Current Detect Control

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