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CY29976
Document #: 38-07413 Rev. *A
Page 5 of 10
SYNC Output
In situations were output frequency relationships are not inte-
ger multiples of each other the SYNC output provides a signal
for system synchronization. The CY29976 monitors the rela-
tionship between the QA and the QC output clocks. It provides
a low going pulse, one period in duration, one period prior to
the coincident rising edges of the QA and QC outputs. The
duration and the placement of the pulse depend on the higher
of the QA and QC output frequencies. The following timing
diagram (Figure 1) illustrates various waveforms for the SYNC
output. Note that the SYNC output is defined for all possible
combinations of the QA and QC outputs even though under
some relationships the lower frequency clock could be used
as a synchronizing signal.
SYNC
QC
QA
SYNC
QC
QA
SYNC
QA
QC
SYNC
QC
QA
SYNC
QA
QC
SYNC
QC
QA
SYNC
QC
QA
VCO
1:1 Mode
2:1 Mode
3:1 Mode
3:2 Mode
4:1 Mode
4:3 Mode
6:1 Mode
Figure 1.
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