CY29972

Document #: 38-07290 Rev. *E

Page 6 of 13

SYNC Output

In situations where output frequency relationships are not integer

multiples of each other, the SYNC output provides a signal for

system synchronization. The CY29972 monitors the relationship

between the QA and 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

placement of the pulse depend on the higher of the QA and QC

output frequencies. The following timing diagram illustrates

various waveforms for the SYNC output. Note that the SYNC

output is defined for all possible combinations of 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. Timing Diagram

[+] Feedback