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BCK
FSYNC
LRCK
DOUT
t
(CKFS)
t
(BCKH)
t
(BCKL)
t
(CKLR)
t
(LRCP)
t
(BCKP)
t
(CKDO)
t
(LRDO)
0.5 V
DD
0.5 V
DD
0.5 V
DD
0.5 V
DD
t
(FSYP)
T0018-01
Synchronization With Digital Audio System
PCM1802
SLES023C – DECEMBER 2001 – REVISED JANUARY 2005
PARAMETER MIN TYP MAX UNIT
t
(BCKP)
BCK period 150 1/(64 f
S
) 1200 ns
t
(BCKH)
BCK pulse duration, high 75 600 ns
t
(BCKL)
BCK pulse duration, low 75 600 ns
t
(CKLR)
Delay time, BCK falling edge to LRCK valid –10 20 ns
t
(LRCP)
LRCK period 10 1/f
S
80 µ s
t
(CKFS)
Delay time, BCK falling edge to FSYNC valid –10 20 ns
t
(FSYP)
FSYNC period 5 1/(2 f
S
) 40 µ s
t
(CKDO)
Delay time, BCK falling edge to DOUT valid –10 20 ns
t
(LRDO)
Delay time, LRCK edge to DOUT valid –10 20 ns
t
r
Rise time of all signals 10 ns
t
f
Fall time of all signals 10 ns
NOTE: Timing measurement reference level is (V
IH
+ V
IL
) / 2. Rise and fall times are measured from 10% to 90% of IN/OUT
signal swing. Load capacitance of all signals is 20 pF.
Figure 27. Audio Data Interface Timing (Master Mode: FSYNC, LRCK, and BCK Work as Outputs)
In slave mode, the PCM1802 operates under LRCK, synchronized with system clock SCKI. The PCM1802 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 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/f
S
and digital output is forced into BPZ code until resynchronization between LRCK and SCKI is completed.
In the case of changes less than ± 5 BCKs for 64 BCK/frame ( ± 4 BCKs for 48 BCK/frame), resynchronization
does not occur.
Figure 28 illustrates the digital output response for loss of synchronization and resynchronization. During
undefined data, some noise might be generated in the audio signal. Also, the transition of normal to undefined
data and undefined or zero data to normal creates a data discontinuity in the digital output, which can generate
some noise in the audio signal.
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