32/fS

T0082-01

48/fin or 48/fS

Fade-In Start

Fade-In Complete

DOUT

DOUT

(Contents)

Normal Data

Synchronization Lost

Synchronous

1/fS

BPZ

State of

Synchronization

Asynchronous

Synchronous

Resynchronization

Synchronization Lost

Asynchronous

Resynchronization

Synchronous

Normal Data

Undefined

Data

Normal Data

Zero Data

Zero Data

Normal Data

48/fin or 48/fS

Fade-In Restart

32/fS

PCM1808-Q1

SLES265A – MARCH 2011 – REVISED AUGUST 2012

www.ti.com

SYNCHRONIZATION WITH DIGITAL AUDIO SYSTEM

In slave mode, the PCM1808-Q1 operates under LRCK (pin 7), synchronized with system clock SCKI (pin 6).

The PCM1808-Q1 does not require a specific phase relationship between LRCK and SCKI, but does require the

synchronization of LRCK and SCKI.

If the relationship between LRCK and SCKI changes more than ±6 BCKs for 64 BCK/frame (±5 BCKs for 48

BCK/frame) during one sample period due to LRCK or SCKI jitter, internal operation of the ADC halts within 1/fS

and digital output is forced to zero data (BPZ code) until resynchronization between LRCK and SCKI is

established.

In the case of changes less than ±5 BCKs for 64 BCK/frame (±4 BCKs for 48 BCK/frame), resynchronization

does not occur and the previously described digital output control and discontinuity do not occur.

Figure 25 illustrates the digital output response for loss of synchronization and resynchronization. During

undefined data, the PCM1808-Q1 can generate some noise in the audio signal. Also, the transition of normal

data to undefined data creates a discontinuity in the digital output data, which can generate some noise in the

audio signal. The digital output is valid after resynchronization completes and the time of 32/fS has elapsed.

Because the fade-in operation is performed, it takes additional time of 48/fin or 48/fS until the level corresponding

to the analog input signal is obtained. If synchronization is lost during the fade-in or fade-out operation, the

operation stops and DOUT (pin 9) is forced to zero data immediately. The fade-in operation resumes from mute

after the time of 32/fS following resynchronization.

Figure 25. ADC Digital Output for Loss of Synchronization and Resynchronization

18

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