WM8994ECSSLASHR datasheet(222/363 Pages) CIRRUS

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WM8994

222

Rev 4.6

DEFAULT SEQUENCES

When the WM8994 is powered up, a number of Control Write Sequences are available through

default settings in the sequencer memory locations. The pre-programmed default settings include

Start-Up and Shut-Down sequences for each of the output drivers. Note that the default sequences do

not include audio signal path or gain setting configuration; this must be implemented prior to

scheduling any of the default Start-Up sequences.

The entire sequencer memory m

ay be programmed to users’ own settings at any time, as described in

“Programming a Sequence”. Users’ own settings remain in memory regardless of WSEQ_ENA, and

are not affected by software resets (i.e. writing to Register R0). However, any non-default sequences

are lost when the device is powered down.

The following default control sequences are provided:

Headphone Cold Start-Up - This sequence powers up the headphone driver and charge pump. It

commands the DC Servo to perform offset correction. It enables the master bias required for

analogue functions. This sequence is intended for enabling the headphone output after initial

power-on, when DC offset correction has not previously been run.

Headphone Warm Start-Up - This sequence is similar to the Headphone Cold Start-Up, but does

not include the DC Servo operation. This sequence is intended for fast enabling of the

headphone output when DC offset correction has previously been scheduled and provided the

analogue gain settings have not been updated since scheduling the DC offset correction.

Speaker Start-Up - This sequence powers up the stereo speaker driver. It also enables the

master bias required for analogue functions.

Earpiece Start-Up - This sequence powers up the earpiece driver. It also enables the master bias

required for analogue functions. The soft-start VMID option is used in order to suppress pops

when the driver is enabled. This sequence is intended for enabling the earpiece driver when the

master bias has not previously been enabled.

Line Output Start-Up - This sequence powers up the line outputs. Active discharge of the line

outputs is selected, followed by the soft-start VMID enable, followed by selection of the master

bias and un-muting of the line outputs. This sequence is intended for enabling the line drivers

when the master bias has not previously been enabled.

Speaker and Headphone Fast Shut-Down - This sequence implements a fast shutdown of the

speaker and headphone drivers. It also disables the DC Servo and charge pump circuits, and

disables the analogue bias circuits using the soft-start (ramp) feature. This sequence is intended

as a shut-down sequence when only the speaker or headphone drivers are enabled.

Generic Shut-Down - This sequence shuts down all of the WM8994 output drivers, DC Servo,

charge pump and analogue bias circuits. It is similar to the Fast Shut-Down sequence, with the

additional control of the earpiece and line output drivers. Active discharge of the line outputs is

included and all drivers are disabled as part of this sequence.

Specific details of each of these sequences is provided below.

Headphone Cold Start-Up

The Headphone Cold Start-Up sequence is initiated by writing 8100h to Register 272 (0110h). This

single operation starts the Control Write Sequencer at Index Address 0 (00h) and executes the

sequence defined in Table 123.

This sequence takes approximately 296ms to run.

WM8994ECS/R 数据表(PDF) 222 Page - Cirrus Logic

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