ICS87952AYI-147 REVISION C AUGUST 4, 2009 8 ©2009 Integrated Device Technology, Inc.
ICS87952I-147 Data Sheet LOW SKEW, 1-TO-11 LVCMOS/LVTTL CLOCK MULTIPLIER/ZERO DELAY BUFFER
Other
signals
Pin 1
C1
GND
C3
50 Ohm
Trace
R7 C11
C5
C6
C2
VDD
50 Ohm
Trace
U1
R2
C16
VCCA
R1
VIA
C4
The following component footprints are used in this layout
example:
All the resistors and capacitors are size 0603.
POWER AND GROUNDING
Place the decoupling capacitors as close as possible to the power
pins. If space allows, placement of the decoupling capacitor on the
component side is preferred. This can reduce unwanted inductance
between the decoupling capacitor and the power pin caused by the
via.
Maximize the power and ground pad sizes and number of vias
capacitors. This can reduce the inductance between the power and
ground planes and the component power and ground pins.
The RC filter consisting of R7, C11, and C16 should be placed as
close to the V
DDA
pin as possible.
CLOCK T RACES AND T ERMINATION
Poor signal integrity can degrade the system performance or cause
system failure. In synchronous high-speed digital systems, the clock
signal is less tolerant to poor signal integrity than other signals. Any
ringing on the rising or falling edge or excessive ring back can
cause system failure. The shape of the trace and the trace delay
might be restricted by the available space on the board and the
component location. While routing the traces, the clock signal traces
should be routed first and should be locked prior to routing other
signal traces.
• The 50Ω output traces should have same length.
• Avoid sharp angles on the clock trace. Sharp angle turns
cause the characteristic impedance to change on the trans
mission lines.
• Keep the clock traces on the same layer. Whenever pos
sible, avoid placing vias on the clock traces. Placement of
vias on the traces can affect the trace characteristic imped
ance and hence degrade signal integrity.
• To prevent cross talk, avoid routing other signal traces in
parallel with the clock traces. If running parallel traces is
unavoidable, allow a separation of at least three trace
widths between the differential clock trace and the other
signal trace.
• The series termination resistors should be located as close to
the driver pins as possible.
FIGURE 2B. PCB BOARD LAYOUT FOR ICS87952I-147
