WM5102 datasheet(186/334 Pages) WOLFSON

186 / 334 page

WM5102

Production Data

PD, June 2014, Rev 4.2

186

The HP1L_ENA and HP1R_ENA register bits are defined in Table 59. The RMV_SHRT_HP1L and

RMV_SHRT_HP1R register bits are defined in Table 79.

Note that, when configuring the RMV_SHRT_HP1L or RMV_SHRT_HP1R bits, care is required not to

change the value of other bits in the register, which may have changed from the default setting.

Accordingly, a ‘read-modify-write’ sequence is required to implement this.

The applicable headphone output(s) configuration must be maintained until after the headphone

detection has completed.

DESCRIPTION

REQUIREMENT

Impedance measurement on HPOUT1L

HP1L_ENA = 0

RMV_SHRT_HP1L = 1

Impedance measurement on HPOUT1R

HP1R_ENA = 0

RMV_SHRT_HP1R = 1

Table 77 Output Configuration for Headphone Detect

When headphone detection is commanded, the WM5102 uses an adjustable current source to

determine the connected impedance. A sweep of measurement currents is applied. The rate of this

sweep can be adjusted using the HP_RATE register. To avoid audible clicks, the default step size

should always be used (HP_RATE = 0).

The timing of the current source ramp is also controlled by the HP_HOLDTIME register. It is

recommended that the default setting (001b) be used for this parameter.

Completion of each measurement is indicated by the HP_DONE register bit. When this bit is set, the

measurement result can be read from the HP_DACVAL register. Note that the decoding equation of

this register (to convert into ‘ohms’) varies according to the HP_IMPEDANCE_RANGE setting.

HEADPHONE IMPEDANCE MEASUREMENT

Trigger the HP measurement, with HP_IMPEDANCE_RANGE = 00

If the HP_DACVAL result >= 100, then decode the impedance as follows:

Otherwise, proceed to step 3.

Trigger the HP measurement, with HP_IMPEDANCE_RANGE = 01

If the HP_DACVAL result >= 169, then decode the impedance as follows:

Otherwise, proceed to step 5.

Trigger the HP measurement, with HP_IMPEDANCE_RANGE = 10

If the HP_DACVAL result >= 169, then decode the impedance as follows:

Otherwise, the impedance is out of range (too high).

Table 78 Headphone Impedance Measurement Control Sequence

Each measurement is triggered by writing ‘1’ to the HP_POLL bit. Completion of each measurement is

indicated by the HP_DONE register bit. Note that, after the HP_DONE bit has been asserted, it will

remain asserted until the next measurement has been commanded.

The headphone detection function is an input to the Interrupt control circuit and can be used to trigger

an Interrupt event on completion of the headphone detection - see “Interrupts”.

WM5102 Datasheet(PDF) 186 Page - Wolfson Microelectronics plc

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