PMC-Sierra, Inc.
STANDARD PRODUCT
PM5945 -UTP5
PMC-940202 ISSUE 2. APRIL 7, 1995
APP_SAPI_UTP5
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• The oscillator used is a 14 pin DIP package. The connections to the oscillator is
setup so that an oscillator with a smaller footprint (8 pin) can also be plugged in
to save board space.
Power, Ground, and Decoupling Capacitors
Only one supply voltage, nominally +5 Volts, is used by all devices on the board and
referenced to by all PECL signals. One solid ground plane is also used. Ferrite
beads are deployed to prevent digital noise from entering analog circuits of both the
S/UNI and the TWISTER devices.
Bypass capacitors can supply transient current and help filter out power and ground
noise. They are placed as close to the pins as possible. Minimum of one 0.1 uF
bypass capacitor per device is used. Wherever possible, one 0.1 uF bypass
capacitor is placed at each power pin of each IC. For high speed IC's, such as the
CY7B951, an additional 0.01 uF bypass capacitor is added to each power pin. A 10
uF electrolytic bypass capacitor is also deployed by the S/UNI, the oscillator, and the
CY7B951 devices. A large electrolytic bypass capacitor (47 to 100 uF) should be
placed as near the power supply as possible.
Special Power and Ground Requirements of CY7B951
A special power plane is provided on the component side for the Cypress CY7B951
device. The power plane under the IC provides a low impedance path connecting
pin 6, 17, and 19.
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PMC [ PMC-SIERRA, INC ]
