873990AY

www.icst.com/products/hiperclocks.html

REV. B

JUNE 13, 2005

9

Integrated

Circuit

Systems, Inc.

ICS873990

V

50

Ω

50

Ω

RTT

Z

Z

FOUT

FIN

RTT =

Z

o

1

((V

3.3V

125

Ω

125

Ω

84

Ω

84

Ω

Z

Z

FOUT

FIN

The clock layout topology shown below is a typical termina-

tion for LVPECL outputs. The two different layouts mentioned

are recommended only as guidelines.

FOUT and nFOUT are low impedance follower outputs that gen-

erate ECL/LVPECL compatible outputs. Therefore, terminating

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

be used for functionality. These outputs are designed to drive

50

Ω transmission lines. Matched impedance techniques should

be used to maximize operating frequency and minimize signal

distortion.

Figures 3A and 3B 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.

As in any high speed analog circuitry, the power supply pins

are vulnerable to random noise. The ICS873990 provides sepa-

rate power supplies to isolate any high switching

noise from the outputs to the internal PLL. V

should be individually connected to the power supply

plane through vias, and bypass capacitors should be

used for each pin. To achieve optimum jitter performance,

power supply isolation is required.

Figure 2 illustrates how

a 10

Ω resistor along with a 10μF and a .01μF bypass

capacitor should be connected to each V

10

Ω

V

CCA

10

μF

.01

μF

3.3V

.01

μF

V

CC