87159AG
www.idt.com
REV. B JULY 25, 2010
ICS87159
1-TO-8 LVPECL-TO-HCSL
÷1, ÷2, ÷4 CLOCK GENERATOR
11
Power and Ground
This section provides a layout guide related to power, ground
and placement of bypass capacitors for a high-speed digi-
tal IC. This layout guide is a general recommendation. The
actual board design will depend on the component types
being used, the board density and cost constraints. The
description assumes that the board has clean power and
ground planes. The principle is to minimize the ESR be-
tween the clean power/ground plane and the IC power/
ground pin.
A low ESR bypass capacitor should be used on each power
pin. The value of bypass capacitors ranges from 0.01uF to
0.1uF. The bypass capacitors should be located as close
IC
C
VIA
GND Pin
Power
Pin
GND
Pads
POWER
Pads
FIGURE 4. RECOMMENDED LAYOUT OF BYPASS CAPACITOR PLACEMENT
to the power pin as possible. It is preferable to locate the
bypass capacitor on the same side as the IC. Figure 4 shows
suggested capacitor placement. Placing the by-
pass capacitor on the same side as IC allows the capaci-tor
to have direct contact with the IC power pin. This can avoid
any vias between the bypass capacitor and the IC power
pins.
The vias should be place at the Power/Ground pads. There
should be minimum one via per pin. Increase the number of
vias from the Power/Ground pads to Power/Ground planes
can improve the conductivity.