843021AG

www.icst.com/products/hiperclocks.html

REV. C MARCH 31, 2005

6

Integrated

Circuit

Systems, Inc.

ICS843021

The ICS843021 has been characterized with 18pF parallel

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

Figure 2 below were determined using a 25MHz, 18pF parallel

resonant 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 ICS843021 provides sepa-

rate power supplies to isolate any high switching

noise from the outputs to the internal PLL. V

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 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

CCA

10

μF

.01

μF

3.3V

.01

μF

V

CC

C1

33p

X1

18pF Parallel Crystal

C2

27p

XTAL_OUT

XTAL_IN