TAS5508 datasheet(45/105 Pages) TI

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3.2.2

Power Down (PDN)

TAS5508

8-Channel Digital Audio PWM Processor

www.ti.com

SLES091D – FEBRUARY 2004 – REVISED JULY 2009

Table 3-2. Values Set During Reset (continued)

CONTROL

SETTING

Bass filter sets

Filter set 3

Loudness (5508)

Loudness disabled, default values

AM interference enable

Disabled

AM interference IF

455

AM interference select sequence

Tuned frequency and mode

0000, BCD

Subwoofer PSVC control

Enabled

PSVC and PSVC range

Disabled/0 dB

After the initialization time, the TAS5508 starts the transition to the operational state with the master

volume set at mute.

Because the TAS5508 has an external crystal time base, following the release of RESET, the TAS5508

sets the MCLK and data rates and performs the initialization sequences. The PWM outputs are held at a

mute state until the master volume is set to a value other than mute via I2C.

The TAS5508 can be placed into the power-down mode by holding the PDN terminal low. When the

power-down mode is entered, both the PLL and the oscillator are shut down. Volume is immediately set to

full attenuation (there is no ramp down). This control uses the PWM mute sequence that provides a low

click and pop transition to the hard mute state (M). A detailed description of the PWM mute sequence is

contained in the PWM section.

Power down is an asynchronous operation that does not require MCLK to go into the power-down state.

To initiate the power-up sequence requires MCLK to be operational and the TAS5508 to receive 5 MCLKs

prior to the release of PDN.

As long as the PDN terminal is held low, the device is in the power-down state with the PWM outputs in a

hard mute (M) state. During power down, all I2C and serial data bus operations are ignored. Table 3-3

shows the device output signals while PDN is active.

Table 3-3. Device Outputs During Power Down

SIGNAL

SIGNAL STATE

Valid

Low

PWM P-outputs

M-state = low

PWM M-outputs

M-state = low

SDA

Signal input

PSVC

M-state = low

Following the application of PDN, the TAS5508 does not perform a quiet shutdown to prevent clicks and

pops produced during the application (the leading edge) of this command. The application of PDN

immediately performs a PWM stop. A quiet stop sequence can be performed by first applying MUTE

before PDN.

When PDN is released, the system goes to the end state specified by MUTE and BKND_ERR pins and

the I2C register settings.

The crystal time base allows the TAS5508 to determine the CLK rates. Once these rates are determined,

the TAS5508 unmutes the audio.

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