ICS601-21 Preliminary
1
Revision 010405
Integrated Circuit Systems, Inc.
l
525 Race Street, San Jose, CA 95126
l
tel (408) 297-1201
l
www.icst.com
ICS601-21 Demo Board Instructions
ICS601-21 Demo Board
The ICS601-21 demo board provides a way to quickly evaluate the performance of the ICS601-21 Low
Phase Noise Clock Multiplier.
Power
Connect either 3.3 volts across the VDD and GND header pins.
Frequency Selection
The output frequency can be changed by setting S0, S1 and S2 on SW1 according to the information in the
Multiplier Select Table on page 2 of the datasheet. Alternatively, shunts can be soldered to the appropriate
0604 device landings underneath SW1. Turning on a switch or stuffing a shunt will pull that particular input
low. Opening the switch or removing the shunt will allow the on-chip pull-up resistors to take the input high.
Input Options
The ICS601-21 Demo board supports either a thru hole or an SMT crystal or a single ended clock input.
Crystal Tuning
In order to achieve 0 PPM frequency synthesis, the ICS601-21 supports external tuning capacitors (C1 and
C2). For exact tuning when using a crystal, capacitors should be connected from pins X1 to ground and X2
to ground. The value of these capacitors is given by the following equation, where C
L
is the specified
crystal load capacitance in pF:
C1 and C2 (pF) = (C
L
- 5) x 2.
So, for a crystal with 16 pF load capacitance, use two 22 pF caps.
Output Termination
The 50 ohm resistors R3 and R5 as serve as termination resistors to ground. These values match the
PCB’s trace impedance. Component locations R2 and R4 are provided to allow for user experimentation.
This “on-board” termination allows the clock outputs to be measured directly with a high impedance
oscilloscope probe. To use “off-board” termination, remove R3 and R5, connect 50 ohm coax cables
between the clock connectors and the oscilloscope and terminate with 50 ohms in the oscilloscope.
Trace Impedance
The ICS601-21 board has controlled impedance traces of 50 ohms for all clock inputs and outputs.
Component
Crystal Input
50 ohm Clock Input
CN1
open
SMA connector
R1
open
short
C2
open
50 ohm
Y1/Y2
stuff only one
open
