WM8994ECSSLASHR datasheet(46/363 Pages) CIRRUS

46 / 363 page

WM8994

Rev 4.6

ADDRESS

BIT

LABEL

DEFAULT

DESCRIPTION

(0001h)

Power

Managem

ent (1)

MICB2_ENA

Microphone Bias 2 Enable

0 = Disabled

1 = Enabled

MICB1_ENA

Microphone Bias 1 Enable

0 = Disabled

1 = Enabled

R57

(0039h)

AntiPOP

(2)

MICB2_DISCH

Microphone Bias 2 Discharge

0 = MICBIAS2 floating when disabled

1 = MICBIAS2 discharged when disabled

MICB1_DISCH

Microphone Bias 1 Discharge

0 = MICBIAS1 floating when disabled

1 = MICBIAS1 discharged when disabled

R58

(003Ah)

MICBIAS

MICB2_LVL

Microphone Bias 2 Voltage Control

0 = 0.9 * AVDD1

1 = 0.65 * AVDD1

MICB1_LVL

Microphone Bias 1 Voltage Control

0 = 0.9 * AVDD1

1 = 0.65 * AVDD1

Table 1 Microphone Bias Control

Note that the maximum source current capability for MICBIAS1 and MICBIAS2 is 2.4mA each. The

external biasing resistance must be large enough to limit each MICBIAS current to 2.4mA across the

full microphone impedance range.

An external capacitor is required on MICBIAS1 and MICBIAS2 in order to ensure accuracy and

stability of each regulator. The recommended capacitance is 4.7

F in each case. See “Recommended

External Components

” for further details.

Note that, if the MICBIAS1 or MICBIAS2 regulator is not enabled, then no external capacitor is

required on the respective MICBIAS pin.

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 MICD_ENA bit; the current thresholds are selected by the

MICD_THR and MICD_SCTHR register fields as described in Table 83

. See “General Purpose

Input/Output

” for a full description of these fields.

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