Datasheet

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SLES105B − FEBRUARY 2004 − REVISED NOVEMBER 2006
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17
AUDIO DATA INTERFACE
Audio Serial Interface
The audio interface port is a 3-wire serial port. It includes LRCK (pin 4), BCK (pin 6), and DATA (pin 5). BCK is the serial
audio bit clock, and it is used to clock the serial data present on DATA into the serial shift register of the audio interface.
Serial data is clocked into the PCM1792A on the rising edge of BCK. LRCK is the serial audio left/right word clock.
The PCM1792A requires the synchronization of LRCK and system clock, but does not need a specific phase relation
between LRCK and system clock.
If the relationship between LRCK and system clock changes more than ±6 BCK, internal operation is initialized within 1/f
S
and analog outputs are forced to the bipolar zero level until resynchronization between LRCK and system clock is
completed.
PCM Audio Data Formats and Timing
The PCM1792A supports industry-standard audio data formats, including standard right-justified, I
2
S, and left-justified. The
data formats are shown in Figure 28. Data formats are selected using the format bits, FMT[2:0], in control register 18. The
default data format is 24-bit I
2
S. All formats require binary 2s complement, MSB-first audio data. Figure 27 shows a detailed
timing diagram for the serial audio interface.
DATA
t
(BCH)
50% of V
DD
BCK
LRCK
t
(BCL)
t
(LB)
t
(BCY)
t
(DS)
t
(DH)
50% of V
DD
50% of V
DD
t
(BL)
PARAMETERS MIN MAX UNITS
t
(BCY)
BCK pulse cycle time 70 ns
t
(BCL)
BCK pulse duration, LOW 30 ns
t
(BCH)
BCK pulse duration, HIGH 30 ns
t
(BL)
BCK rising edge to LRCK edge 10 ns
t
(LB)
LRCK edge to BCK rising edge 10 ns
t
(DS)
DATA setup time 10 ns
t
(DH)
DATA hold time 10 ns
— LRCK clock duty 50% ± 2 bit clocks
Figure 27. Timing of Audio Interface