WM1811A datasheet(131/328 Pages) WOLFSON

131 / 328 page

Production Data

WM1811A

PD, November 2013, Rev 4.1

131

EXTERNAL ACCESSORY DETECTION

The WM1811A provides external accessory detection functions which can sense the presence and

impedance of external components. This can be used to detect the insertion or removal of an external

headphone or headset, and to provide an indication of key/button push events.

Jack insertion is detected using the JACKDET pin, which must be connected to switch contacts within

the jack socket. An Interrupt event is generated whenever a jack insertion or jack removal event is

detected.

Microphones, push-buttons and other accessories can be detected via the MICDET pin. The presence

of a microphone, and the status of a hookswitch can be detected. This feature can also be used to

detect push-button operation.

Note that clocking is required for all of the external accessory detection functions.The WM1811A can

support accessory detection using a low frequency (eg. 32kHz) clock for reduced power consumption.

JACK DETECT

The WM1811A provides support for jack insertion switch detection. The Jack Detect function also

enables the device to be configured for low power standby modes; typical use cases are where an

application is idle in standby mode until a headphone or headset jack is inserted.

Jack insertion and removal is detected using the JACKDET pin. The recommended external

connection circuit is illustrated in Figure 39. The status of the jack insertion switch can be read using

the JACKDET_LVL register.

The JACKDET input de-bounce is enabled or disabled using the JACKDET_DB register, as described

in Table 77.

The Jack Detect function is enabled whenever JACKDET_MODE > 00. An Interrupt Request (IRQ)

event is generated whenever a jack insertion or jack removal is detected (see “Interrupts”).

Different settings of JACKDET_MODE allow different low power configurations to be selected. Note

that audio and/or microphone detection functions are not supported under these low power conditions.

The options provided by the JACKDET_MODE register are summarised in Table 76.

When JACKDET_MODE = 01, the LDO1 regulator output must be configured to be floating when

disabled. The LDO1_DISCH bit (see Table 127) must be set to 0 before setting

JACKDET_MODE = 01.

Note that, in modes where MICDET (microphone / accessory detect) functionality is required, this

must be configured as described in the following section. In modes where the Audio functions are not

supported, none of the WM1811A analogue/digital audio record or playback functions are possible.

JACKDET_MODE

JACK DETECT

MICROPHONE /

ACCESSORY

DETECT

AUDIO

FUNCTIONS

TYPICAL USE CASE



Full device operation (eg. audio record/playback).

(Note that Jack Detect is not supported.)



Device in idle mode, monitoring accessory activity

(eg. button press, jack removal etc.)



Device in standby mode, awaiting jack insertion -

Lowest power external accessory detection mode.



Full device operation (eg. audio record/playback).

Note that JACKDET_MODE = 01 or 10 are not supported if AVDD1 or DCVDD is supplied externally.

These settings must not be selected if AVDD1 or DCVDD is supplied externally (ie. if LDO1 or LDO2 is not used).

Table 76 Jack Detect Modes

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