WM8281ECSSLASHR datasheet(208/392 Pages) CIRRUS

208 / 392 page

WM8281

208

Rev 4.0

The control registers associated with the MICDET Clamp and General Purpose Switch functions are

described in Table 76.

ADDRESS

BIT

LABEL

DEFAULT

DESCRIPTION

R674

(02A2h)

Micd Clamp

control

3:0

MICD_CLAMP_M

ODE [3:0]

0000

MICDET Clamp Mode

0h = Disabled

1h = Active (MICDET1 and MICDET2

are shorted together)

2h = Reserved

3h = Reserved

4h = Active when JD1=0

5h = Active when JD1=1

6h = Active when GP5=0

7h = Active when GP5=1

8h = Active when JD1=0 or GP5=0

9h = Active when JD1=0 or GP5=1

Ah = Active when JD1=1 or GP5=0

Bh = Active when JD1=1 or GP5=1

Ch = Active when JD1=0 and GP5=0

Dh = Active when JD1=0 and GP5=1

Eh = Active when JD1=1 and GP5=0

Fh = Active when JD1=1 and GP5=1

R3096

(0C18h)

GP Switch 1

1:0

SW1_MODE [1:0]

General Purpose Switch control

00 = Disabled (open)

01 = Enabled (closed)

10 = Enabled when MICDET Clamp is

active

11 = Enabled when MICDET Clamp is

not active

R3413

(0D55h)

AOD IRQ

Raw Status

MICD_CLAMP_S

MICDET Clamp status

0 = Clamp not active

1 = Clamp active

R3414

(0D56h)

Jack detect

debounce

MICD_CLAMP_D

MICDET Clamp de-bounce

0 = Disabled

1 = Enabled

Table 76 MICDET Clamp and General Purpose Switch control

MICROPHONE DETECT

The WM8281 microphone detection circuit measures the impedance of an external load connected to

one of the MICDET pins. This feature can be used to detect the presence of a microphone, and the

status of the associated hookswitch. It can also be used to detect push-button status or the

connection of other external accessories.

The microphone detection circuit measures the impedance connected to MICDET1 or MICDET2. In

the discrete measurement mode (ACCDET_MODE=000), the function reports whether the measured

impedance

lies

within

one

pre-defined

levels.

the

ADC

measurement

mode

(ACCDET_MODE=111), a more specific result is provided in the form of a 7-bit ADC output.

The microphone detection circuit typically uses one of the MICBIAS outputs as a reference. The

WM8281 will automatically enable the appropriate MICBIAS when required in order to perform the

detection function; this allows the detection function to be supported in low-power standby operating

conditions.

Note that the MICVDD power domain must be enabled when using the microphone detection function.

This power domain is provided using an internal Charge Pump (CP2) and LDO Regulator (LDO2).

See “Charge Pumps, Regulators and Voltage Reference” for details of these circuits.

To select microphone detection on one of the MICDET pins, the ACCDET_MODE register must be

set to 000 or 111 (depending on the desired measurement mode). The ACCDET_MODE register is

defined in Table 77.

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