ZL30406

Data Sheet

6

Zarlink Semiconductor Inc.

1.4

Output Interface Circuit

The output of the VCO is used by the Output Interface Circuit to provide four LVPECL differential clocks at

77.76 MHz, one programmable CML differential clock (19.44 MHz, 38.88 MHz, 77.76 MHz, 155.52 MHz) controlled

with FS1-2 pins and a single-ended 19.44 MHz output clock. This block provides also a 19.44 MHz feedback clock

that closes PLL loop. Each output clock can be enabled or disabled individually with the associated Output Enable

pin.

To reduce power consumption and achieve the lowest possible intrinsic jitter the unused output clocks must be

disabled. If any of the LVPECL outputs are disabled they must be left open without any terminations.

The output clock frequency of the OC-CLKo CML differential output clock is selected with FS1-2 pins as shown in

the following table.

Output Clocks

Output Enable Pins

C77oP/N-A

C77oEN-A

C77oP/N-B

C77oEN-B

C77oP/N-C

C77oEN-C

C77oP/N-D

C77oEN-D

OC-CLKoP/N

OC-CLKoEN

C19o

C19oEN

Table 1 - Output Enable Control

FS2

FS1

OC-CLKo

Frequency

0

0

19.44 MHz

0

1

38.88 MHz

1

0

77.76 MHz

1

1

155.52 MHz

Table 2 - OC-CLKo Clock Frequency Selection