mc68336 Freescale Semiconductor, Inc, mc68336 Datasheet - Page 10

• Manufacturer Part Number: mc68336
• Description: An Introduction To The Mc68331 And Mc68332
• Manufacturer: Freescale Semiconductor, Inc

circuit board. If the dirt or grime that form the high resistance path is on an inner layer of the printed circuit
board, the board is unusable. If the leakage is due to condensation on the board, then spray the oscillator
circuit with a protective epoxy.
2.5.2.3 Layout and Strange Behavior
Oscillator layout is just as important as a good quality crystal and cleanliness in manufacturing the printed
circuit board. The best possible solution is to use a multi-layer board with a separate ground plane. The rules
for oscillator layout are quite simple. First, locate the crystal and all associated external components as
close to the oscillator pins as possible. Second, do not under any circumstance run a high frequency trace
under either the feedback or series resistor or the crystal. Third, if there is no separate ground plane, make
sure that the ground for the bypass capacitors is connected to a solid ground trace. Figure 6 shows typical
one-layer oscillator layout.
10
C
bypass
Freescale Semiconductor, Inc.
Figure 6 Typical One-Layer Oscillator Layout
For More Information On This Product,
Figure 5 DC Model of Oscillator Circuit
TO +5 OR GND
EXTAL
B
XTAL
Go to: www.freescale.com
XTAL
INTERNAL AMPLIFIER
C
GND
C
R
bypass
f
10 M
R
f
10 M
R
R
d
s
XTAL
EXTAL
A
GROUND
PLANE
M68331/332TUT/D
MC68331/332
332TUT XTAL PCB LAYOUT
332TUT XTAL RF/RD CONN