AN2127 Freescale Semiconductor / Motorola, AN2127 Datasheet - Page 12

• Manufacturer Part Number: AN2127
• Description: EMC Guidelines for MPC Based Automotive Powertrain Systems
• Manufacturer: Freescale Semiconductor / Motorola

3.4 Signal Routing and Terminations
3.5 Layer Stack-Up and Vias
Micro-Island
Resistors
Leaving
Signals
High-speed signals should be isolated as much as possible by using spacing and shielding of the signal
traces. High-speed signals should also be routed with minimal lengths. Some high-speed signals such
as CLKOUT and ENGCLK may require a termination resistor to avoid ringing and to help slow down the
edge rate. The optimum value for the termination resistor will depend on the specific application, but
starting with a value of 30
sible to the MCU. Typically, the bus pins do not require termination resistors because the memory chip
is placed within a few inches of the MCU and therefore the one-way propagation delay is less than one-
fourth the signal rise time.
Most MPC500 family applications will require the use of a multi-layer board; four layer boards are the
most common. For multi-layer boards, dedicated power and ground planes should be used. An example
of a good four-layer stack-up is shown in
EMC Guidelines for MPC500-Based Automotive Powertrain Systems
Micro-Island
Figure 7 Typical Micro-Island Approach to Decoupling and Grounding
Freescale Semiconductor, Inc.
For More Information On This Product,
is reasonable. The termination resistors should be located as close as pos-
Rev. 0, 15 July 2001
Filter Components
for Power Supply
Go to: www.freescale.com
MCU
XTAL
Figure
Moat
8.
Memory
Capacitors
MOTOROLA
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