840001AGI

www.icst.com/products/hiperclocks.html

REV. A JUNE 20, 2005

8

Integrated

Circuit

Systems, Inc.

ICS840001I

PRELIMINARY

Figure 3A shows a schematic example of the ICS840001I. An

example of LVCMOS termination is shown in this schematic.

Additional LVCMOS termination approaches are shown in the

LVCMOS Termination Application Note. In this example, an 18

pF parallel resonant 26.5625MHz crystal is used.The C1=27pF

and C2=33pF are recommended for frequency accuracy. For

different board layout, the C1 and C2 may be slightly adjusted

for optimizing frequency accuracy. The output frequency can be

set at either 106.25MHz or 212.5MHz. Leaving the R1 un-in-

stalled (or install 1k

Ω pull-down) will set the output frequency at

106.25MHz. Installing the R1 pull up will set the output frequency

at 212.5MHz.

Figure 3B shows an example of P.C. board layout. The crystal

X1 footprint in this example allows either surface mount (HC49S)

or through hole (HC49) package. C3 is 0805. C1 and C2 are

0402. Other resistors and capacitors are 0603. This layout as-

sumes that the board has clean analog power and ground planes.

LVCMOS

VDD=3.3V

U2

840001I

1

2

3

4

8

7

6

5

VDDA

OE

XTAL_OUT

XTAL_IN

VDD

Q

GND

FREQ_SEL

C5

0.1u

R1

1K

R2

10

C3

10uF

VDD

VDD

C2

33pF

FRE_SEL

VDD

C4

0.1u

Zo = 50 Ohm

OE

Q

R3

43

VDDA

C1

27pF

X1