WM8523 datasheet(27/51 Pages) WOLFSON

27 / 51 page

Production Data

WM8523

PD, Rev 4.1, August 2011

DAC FEATURES

SYSTEM ENABLE

The WM8523 includes a number of enable and disable mechanisms to allow the device to be powered

on and off in a pop-free manner. The SYS_ENA[1:0] control bits enable the DAC and analogue paths.

ADDRESS

BIT

LABEL

DEFAULT

DESCRIPTION

PSCTRL1

02h

1:0

SYS_

ENA[1:0]

System Power Control

00 = Off

01 = Power down

10 = Power up and mute

11 = Power up and unmute

Table 12 System Enable Control

Note: MCLK must be present at all times when using the SYS_ENA[1:0] bits. If MCLK is stopped at any

point the device will power down to the ‘off’ state, but all register settings will remain. Restarting MCLK

will start the device internal power sequence and the device will return to the power state set by the

SYS_ENA[1:0] bits.

The power up and power down sequences are summarised in Figure 23. There is no requirement to

manually cycle the device through the sequence via register writes, as the device will always

automatically step through each stage in the sequence.

Power Up

When SYS_ENA[1:0]=00, the internal clocks are stopped and all analogue and digital blocks are

disabled for maximum power saving. The device starts up in this state in software mode. Setting

SYS_ENA[1:0]=01 enables the internal charge pump and required control circuitry, but the signal path

remains powered down. When SYS_ENA[1:0]=10 all blocks are powered up sequentially and full system

configuration is achieved. Once this is complete, the device is ready to pass audio but is muted. Setting

SYS_ENA[1:0]=11 releases the mute and audio playback begins.

Power Down

When SYS_ENA[1:0]=11 the device is powered up and passing audio. Changing SYS_ENA[1:0]=10

applies a digital softmute to the output. Setting SYS_ENA[1:0]=01 sequentially powers down all circuit

blocks but leaves the charge pump and required control circuitry enabled. This can be considered the

low-power standby state. Finally, setting SYS_ENA[1:0]=00 will disable all circuit blocks including the

charge pump, and full system initialisation will be required to restart the device.

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