WM8281ECSSLASHR datasheet(219/392 Pages) CIRRUS

219 / 392 page

WM8281

Rev 4.0

219

ADDRESS

BIT

LABEL

DEFAULT

DESCRIPTION

R1188

(04A4h)

HP Test Ctrl

1:0

HP1_TST_CAP_

SEL [1:0]

This field must be set to 01 when the

Headphone Detection function is

enabled on HPOUTL or HPOUTR.

This field must be set to 11 (default) at

all other times.

Table 80 Headphone Detect Control

MICDET1/HPOUT1FB2

Headphone Detect /

Impedance measurement

Headphone Detect selected by

ACCDET_MODE

HPDETL

HPDETR

HPOUT1L

HPOUT1R

4.7



4.7



MICDET1/HPOUT1FB2 or

HPOUT1FB1/MICDET2

selected by ACCDET_SRC

(Note: HPOUT1FB* ground

connection close to headset jack)

HPOUT1FB1/MICDET2

Figure 67 Headphone Detect Interface

The external connections for the Headphone Detect circuit are illustrated in Figure 67. Note that only

the HPOUT1L or HPOUT1R headphone outputs should be connected to HPDETL or HPDETR pins -

impedance measurement is not supported on HPOUT2L, HPOUT2R, HPOUT3L or HPOUT3R.

Note that, where external resistors are connected in series with the headphone load, as illustrated, it

is recommended that the HPDETn connection is to the headphone side of the resistors. If the

HPDETn connection is made to the WM8281

‘end’ of these resistors, this will lead to a corresponding

offset in the measured impedance.

Under default conditions, the measurement time varies between 17ms and 61ms according to the

impedance of the external load. A high impedance will be measured faster than a low impedance.

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