840051AG

www.icst.com/products/hiperclocks.html

REV. A JANUARY 14, 2005

7

Integrated

Circuit

Systems, Inc.

ICS840051

The ICS840051 has been characterized with 18pF parallel

resonant crystals. The capacitor values, C1 and C2, shown in

Figure 2 below were determined using an 18pF parallel reso-

nant crystal and were chosen to minimize the ppm error. The

optimum C1 and C2 values can be slightly adjusted for different

board layouts.

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

vulnerable to random noise. The ICS840051 provides separate

power supplies to isolate any high switching noise from the out-

puts to the internal PLL. V

nected to the power supply plane through vias, and bypass ca-

pacitors should be used for each pin. To achieve optimum

jitter performance, power supply isolation is required.

Figure 1

illustrates how a 10

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

bypass capacitor should be connected to each V

10

Ω

V

DDA

10

µF

.01

µF

3.3V

.01

µF

V

DD

C1

33p

X1

18pF Parallel Crystal

C2

22p

XTAL_OUT

XTAL_IN