ICS8431CM-01

www.icst.com/products/hiperclocks.html

REV. A JUNE 5, 2001

8

Integrated

Circuit

Systems, Inc.

ICS8431-01

The clock layout topology shown below is typical for

IA64/32 platforms. The two different layouts mentioned are

recommended only as guidelines.

FOUT and nFOUT are low impedance follower outputs that

generate ECL/PECL compatible outputs. Therefore, terminat-

ing resistors (DC current path to ground) or current sources

must be used for functionality. These outputs are designed to

3.3V

FOUT

FIN

5

Z

o

5

2

Z

o

3

2

Z

o

3

2

Z

Z

Z

Z

RTT =

1

(VOH + VOL / VCC –2) –2

Z

o

Z

Z

50

Ω

50

Ω

RTT

VCC-2V

FIN

FOUT

Z

Z

drive 50

Ω transmission lines. Matched impedance techniques

should be used to maximize operating frequency and mini-

mize signal distortion. There are a few simple termination

schemes.

Figures 5A and 5B show two different layouts which

are recommended only as guidelines. Other suitable clock lay-

outs may exist and it would be recommended that the board

designers simulate to guarantee compatibility across all printed

circuit and clock component process variations.

The schematic of the ICS8431-01 layout example used in this layout guideline is shown in

Figure 6A. The ICS8431-01 recommended

PCB board layout for this example is shown in

Figure 6B. This layout example is used as a general guideline. The layout in the actual

system will depend on the selected component types, the density of the components, the density of the traces, and the stacking of

the P.C. board.

R3

125

C3

0.01uF

X1

U1

8431-01

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

20

21

22

23

24

28

27

26

25

nc

nc

nc

nc

nc

nc

nc

nc

nc

SSC_CTL0

SSC_CTL1

VEE

TEST_IO

VDD

VEE

nFOUT

FOUT

VDDO

nc

nc

VEE

VDDA

nc

nc

nc

VDDI

XTAL2

XTAL1

C1

0.1uF

VDDA

IN+

VDD

IN-

C4

10uF

R4

84

R2

84

R1

50

IN+

VDD

R2

50

R5

10

C6

0.01uF

R3

50

R1

125

VDD

TL2

Zo = 50 Ohm

IN-

VDD0

Termination A

TL1

Zo = 50 Ohm

C2

0.1uF

Termination

B (not shown

in the layout)