PCM1850

PCM1851

SLES108 − MARCH 2004

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21

SYNCHRONIZATION WITH DIGITAL AUDIO SYSTEM

In slave mode, the PCM1850/1851 operates under LRCK, synchronized with system clock SCKI. The PCM1850/1851

does not need 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 BCKs/frame (±5 BCKs for 48 BCKs/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 into the BPZ code until resynchronization between LRCK and SCKI is completed.

In the case of changes less than

±5 BCKs for 64 BCKs/frame (±4BCKs for 48BCK/frame), resynchronization with

simultaneous discontinuity in the digital output does not occur.

Figure 26 illustrates the digital output response for loss of synchronization and resynchronization. During undefined data,

the PCM1850/1851 might generate some noise in the audio signal. Also, the transition of normal to undefined data and

undefined or zero data to normal creates a discontinuity of data in the digital output, which could generate some noise in

the audio signal.

It is recommended to set RST (pin 10) to LOW to get stable analog performance when the sampling rate, interface mode,

or data format is changed.

1/fS

32/fS

NORMAL DATA

ZERO DATA

UNDEFINED

DATA

NORMAL DATA

SYNCHRONOUS

ASYNCHRONOUS

SYNCHRONOUS

Resynchronization

Synchronization Lost

DOUT

State of

Synchronization

Figure 26. ADC Digital Output for Loss of Synchronization and Resynchronization

Power-Down Control

RST(pin 10) controls the entire ADC operation. During reset mode, the supply current of the analog section is shut off and

the digital section is initialized. DOUT (pin 3) is also disabled. Halting SCKI, BCK, and LRCK is recommended to minimize

power dissipation.

RST

POWER-DOWN MODE

LOW

Reset and power-down modes

HIGH

Normal operation mode

Overflow Flag Output

The PCM1850/1851 has an output flag (pin 4) that indicates when overflow occurs in the L-channel or R-channel, and this

flag remains HIGH at least during the 8192/fS time for a momentary overflow occurrence.