Si5321

Rev. 2.3

25

Table 10. Si5321 Pin Descriptions

Pin #

Pin Name

I/O

Signal Level

Description

D1

E1

CLKIN+

CLKIN–

I

AC Coupled

(See Table 2)

System Clock Input.

Clock input to the DSPLL circuitry. The frequency of

the CLKIN signal is multiplied by the DSPLL to gen-

erate the CLKOUT clock output. The input-to-output

frequency multiplication factor is set by selecting the

clock input range and the clock output range. The

frequency of the CLKIN clock input can be in the 19,

38, 77, 155, 311, or 622 MHz range (nominally

19.44, 38.88, 77.76, 155.52, 311.04, or

622.08 MHz) as indicated in Table 3 on page 7. The

clock input frequency is selected using the

INFRQSEL[2:0] pins. The clock output frequency is

selected using the FRQSEL[1:0] pins. An additional

scaling factor may be selected for FEC operation

using the FEC[2:0] control pins.

F1

G1

H1

INFRQSEL[0]

INFRQSEL[1]

INFRQSEL[2]

I*

LVTTL*

Input Frequency Range Select.

Pins(INFRQSEL[2:0]) select the frequency range for

the input clock, CLKIN. (See Table 3 on page 7.)

000 = Reserved.

001 = 19 MHz range.

010 = 38 MHz range.

011 = 77 MHz range.

100=155MHz range.

101=311MHz range.

110 = 622 MHz range.

111 = Reserved.

H6

H7

CLKOUT+

CLKOUT–

OCML

Differential Clock Output.

High-frequency clock output. The frequency of the

CLKOUT output is a multiple of the frequency of the

CLKIN input. The input-to-output frequency multipli-

cation factor is set by selecting the clock input range

and the clock output range. The frequency of the

CLKOUT clock output can be in the 19, 38, 77, 155,

311, 622, 1244 or 2488 MHz range as indicated in

Table 3 on page 7. The clock output frequency is

selected using the FRQSEL[2:0] pins. The clock

input frequency is selected using the

INFRQSEL[2:0] pins. An additional scaling factor

may be selected for FEC operation using the

FEC[2:0] control pins.

*Note:

The LVTTL inputs on the Si5321 device have an internal pulldown mechanism that causes the input to default to a

logic low state if the input is not driven from an external source.