ICS5OSK481 Datasheet, PDF (2/5 Pages) Integrated Circuit Systems – 48 MHz Tiny USB Clock Source

P R E L I M I N A RY I N F O R M AT I O N
Pin Assignment
ICLK 1
GND 2
CLK
3
5
OE
4
VDD
ICS5OSK481
48 MHz Tiny USB Clock Source
Pin Descriptions
Pin
Number
1
Pin
Name
ICLK
2
GND
3
CLK
4
VDD
5
OE
Pin
Type
Input
Power
Output
Power
Input
Pin Description
25 MHz clock input. Connect to a parallel resonant fundamental crystal or
input clock.
Connect to ground.
PLL output clock. Internal pull-down resistor.
Connect to 3.3 V.
Output Enable pin. Internal pull-up resistor. OE=0 outputs tristate with weak
pull-down.
External Components
Decoupling Capacitor
As with any high-performance mixed-signal IC, the
ICS5OSK481 must be isolated from system power
supply noise to perform optimally.
A decoupling capacitor of 0.01µF must be connected
between each VDD and the PCB ground plane.
Series Termination Resistor
Clock output traces over one inch should use series
termination. To series terminate a 50Ω trace (a
commonly used trace impedance), place a 33Ω resistor
in series with the clock line, as close to the clock output
pin as possible. The nominal impedance of the clock
output is 20Ω.
to the VDD pin as possible. No vias should be used
between the decoupling capacitors and VDD pins. The
PCB trace to VDD pins should be kept as short as
possible, as should the PCB trace to the ground via.
2) To minimize EMI, the 33Ω series termination resistor
(if needed) should be placed close to the clock output.
3) An optimum layout is one with all components on the
same side of the board, minimizing vias through other
signal layers. Other signal traces should be routed
away from the ICS5OSK481. This includes signal
traces just underneath the device, or on layers adjacent
to the ground plane layer used by the device.
PCB Layout Recommendations
For optimum device performance and lowest output
phase noise, the following guidelines should be
observed.
1) The 0.01µF decoupling capacitors should be
mounted on the component side of the board as close
MDS 5OSK481 B
2
Revision 111805
Integrated Circuit Systems, Inc. ● 525 Race Street, San Jose, CA 95126 ● tel [phone] ● www.icst.com