CS4299 datasheet(34/52 Pages) CIRRUS

34 / 52 page

CS4299

5.2

Powerdown Controls

The

Powerdown

Control/Status

(Index 26h) controls the power management func-

tions. The PR[6:0] bits in this register control the

internal powerdown states of the CS4299. Power-

down control is available for individual subsections

of the CS4299 by asserting any PRx bit or any com-

bination of PRx bits. Most powerdown states can

be resumed by clearing the corresponding PRx bit.

Table 11 shows the mapping of the power control

bits to the functions they manage.

When PR0 is ‘set’, the L/R ADCs and the Input

Mux are shut down and the ADC bit in the Power-

down Control/Status Register (Index 26h) is

‘cleared’ indicating the ADCs are no longer in a

ready state. The same is true for the DACs, the an-

alog mixers, and the reference voltage (Vrefout).

When the PR2 or PR3 bit of the mixer is ‘cleared’,

the mixer section will begin a power-on process,

and the corresponding powerdown status bit will be

‘set’ when the hardware is ready.

Shutting down the AC-link by ‘setting’ PR4 causes

the primary Codec to turn off the BIT_CLK and

drive SDATA_IN low. It also ignores SYNC and

SDATA_OUT in their normal capacities. Either a

Cold Reset or a Warm Reset is required to restore

operation to the CS4299. A Cold Reset will restore

all mixer registers to their power-on default values.

A Warm Reset will not alter the values of any mix-

er register, except clearing the PR4 bit in Power-

down Control/Status Register (Index 26h).

The PR5 bit powers down all analog and digital

subsections of the device. A Cold Reset is the only

way to restore operation to the CS4299 after a PR5

global powerdown.

The CS4299 does not automatically mute any input

or output when the powerdown bits are ‘set’. The

software driver controlling the AC ’97 device must

manage muting the input and output analog signals

before putting the part into any power management

state. The definition of each PRx bit may affect a

single subsection or a combination of subsections

within the CS4299. Table 12 on page 35 contains

the matrix of subsections affected by the respective

PRx function. Table 13 on page 35 shows the dif-

ferent operating power consumptions levels for dif-

ferent powerdown functions.

PR Bit

Function

PR0

L/R ADCs and Input Mux Powerdown

PR1

Front DACs Powerdown

PR2

Analog Mixer Powerdown (Vref on)

PR3

Analog Mixer Powerdown (Vref off)

PR4

AC-link Powerdown (BIT_CLK off)*

PR5

Internal Clock Disable

PR6

Alternate Line Out Powerdown

* Applies only to primary codec

Table 11. Powerdown PR Bit Functions

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