WM8351 datasheet(99/330 Pages) WOLFSON

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WM8351

PD, April 2012, Rev 4.5

13.12.2 MICROPHONE DETECTION

The WM8351 can detect when a microphone has been plugged in, and/or when the microphone is

short-circuited. It detects these events by comparing the current drawn from the MICBIAS pin against

two thresholds. The thresholds for plug-in detection and short-circuit detection are programmable.

A MICBIAS current above the MCDTHR threshold level is used to indicate that a microphone is

plugged in, and is associated with the CODEC_MICD_EINT interrupt. If the bias current exceeds the

MCDSCTHR limit, this indicates a microphone short-circuit condition, and the WM8351 raises a

CODEC_MICSCD_EINT interrupt. See Section 13.12.7 for further details. Note that the MICBIAS

current thresholds are subject to a wide tolerance - up to +/-50% of the specified value.

Microphone detection requires the internal slow clock to be enabled - see Section 12.3.6.

ADDRESS

BIT

LABEL

DEFAULT

DESCRIPTION

R8 (08h)

Power Mgmt 1

MIC_DET_ENA

Enable MIC detect:

0 = disabled

1 = enabled

R74 (4Ah)

Mic Bias

Control

MIC_DET_ENA

4:2

MCDTHR [2:0]

000

Threshold for bias current detection

000 = 160µA

001 = 330µA

010 = 500µA

011 = 680µA

100 = 850µA

101 = 1000µA

110 = 1200µA

111 = 1400µA

These threshold currents scale

proportionally with AVDD. The values

given are for AVDD=3.3V.

1:0

MCDSCTHR

[1:0]

Threshold for microphone short-circuit

detection

00 = 400µA

01 = 900µA

10 = 1350µA

11 = 1800µA

These threshold currents scale

proportionally with AVDD. The values

given are for AVDD=3.3V.

Note:

MIC_DET_ENA can be accessed through R8 or through R74. Reading from or writing to either

Table 49 Controlling Microphone Bias Current Detection

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