WM8945ECSSLASHR datasheet(106/169 Pages) WOLFSON

106 / 169 page

WM8945

Production Data

PD, May 2011, Rev 4.1

106

RECOMMENDED POWER UP/DOWN SEQUENCE

In order to minimise output pop and click noise, it is recommended that the WM8945 device is

powered up and down using one of the following sequences:

Power Up:

ACTION

LABEL

Turn on external supplies and wait for the

supply voltages to settle.

Reset registers to default state (software reset)

SW_RESET

R0 (00h) [15:0]

Enable speaker and line discharge bits

SPKR_DISCH = 1

SPKL_DISCH = 1

LINEL_DISCH = 1

R42 (2Ah) [7]

R42 (2Ah) [6]

R42 (2Ah) [4]

Enable VMID to speaker and line outputs

SPKR_VMID_OP_ENA = 1

SPKL_VMID_OP_ENA = 1

LINEL_VMID_OP_ENA = 1

R42 (2Ah) [13]

R42 (2Ah) [12]

R42 (2Ah) [10]

Enable VMID Fast Start and Start up Bias

Select Start-Up Bias and set VMID soft start for

start-up ramp

VMID_FAST_START = 1

STARTUP_BIAS_ENA = 1

BIAS_SRC = 1

VMID_RAMP[1:0] = 01

R7 (07h) [11]

R7 (07h) [8]

R7 (07h) [7]

R7 (07h) [6:5]

If using VMID as the reference voltage for the

LDO then select VMID fast start or set to 0 if

using the Bandgap as the reference voltage for

LDO.

Select LDO Start-Up Bias and enable LDO

Delay 300ms for LDO to settle

LDO_REF_SEL_FAST = 1

LDO_BIAS_SRC = 1

LDO_ENA = 1

R53 (35h) [14]

R53 (35h) [5]

R53 (35h) [15]

Enable VMID Buffer and Master Bias

Set VMID_SEL[1:0] for fast start-up

BIAS_ENA = 1

VMID_BUF_ENA = 1

VMID_SEL[1:0] = 11

R2 (02h) [3]

R2 (02h) [2]

R2 (02h) [1:0]

Disable speaker and line discharge bits

SPKP_DISCH = 0

SPKN_DISCH = 0

LINEL_DISCH = 0

R42 (2Ah) [6]

R42 (2Ah) [7]

R42 (2Ah) [4]

Enable speaker mixer and DAC

SPKR_MIX_ENA = 1

SPKL_MIX_ENA = 1

DACR_ENA = 1

DACL_ENA = 1

R3 (03h) [3]

R3 (03h) [2]

R3 (03h) [1]

R3 (03h) [0]

Enable speaker outputs and speaker PGA and

lineout output as required

OUTR_ENA = 1

OUTL_ENA = 1

SPKR_PGA_ENA = 1

SPKL_PGA_ENA = 1

SPKN_OP_ENA = 1

SPKP_OP_ENA = 1

R3 (03h) [15]

R3 (03h) [14]

R3 (03h) [13]

R3 (03h) [12]

R3 (03h) [7]

R3 (03h) [6]

Enable power to speaker drive

SPKR_SPKVDD_ENA = 1

SPKL_ SPKVDD _ENA = 1

R3 (03h) [11]

R3 (03h) [10]

Enable VMID

Delay 150ms to allow VMID to settle

VMID_ENA = 1

R7 (07h) [4]

Set LDO for normal operation

LDO_REF_SEL_FAST = 0

LDO_BIAS_SRC = 0

R53 (35h) [14]

R53 (35h) [5]

Set VMID for normal operation

VMID_FAST_START = 0

STARTUP_BIAS_ENA = 0

R7 (07h) [11]

R7 (07h) [8]

Set VMID divider for normal operation

VMID_SEL = 01

R2 (02h) [1:0]

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