MPC8247 MOTOROLA [Motorola, Inc], MPC8247 Datasheet - Page 13

• Manufacturer Part Number: MPC8247
• Description: MPC8272 PowerQUICC II Family Hardware Specifications
• Manufacturer: MOTOROLA [Motorola, Inc]

4.5
To determine the junction temperature of the device in the application after prototypes are available, the
thermal characterization parameter (
measurement of the temperature at the top center of the package case using the following equation:
where:
The thermal characterization parameter is measured per JEDEC JESD51-2 specification using a 40 gauge
type T thermocouple epoxied to the top center of the package case. The thermocouple should be positioned
so that the thermocouple junction rests on the package. A small amount of epoxy is placed over the
thermocouple junction and over 1 mm of wire extending from the junction. The thermocouple wire is placed
flat against the case to avoid measurement errors caused by cooling effects of the thermocouple wire.
4.6
Each V
should likewise be provided with a low-impedance path to ground. The power supply pins drive distinct
groups of logic on chip. The V
bypass capacitors located as close as possible to the four sides of the package. The capacitor leads and
associated printed circuit traces connecting to chip V
per capacitor lead. A four-layer board employing two inner layers as V
All output pins on the MPC8272 have fast rise and fall times. Printed circuit (PC) trace interconnection
length should be minimized in order to minimize overdamped conditions and reflections caused by these
fast output switching times. This recommendation particularly applies to the address and data buses.
Maximum PC trace lengths of six inches are recommended. Capacitance calculations should consider all
device loads as well as parasitic capacitances due to the PC traces. Attention to proper PCB layout and
bypassing becomes especially critical in systems with higher capacitive loads because these loads create
higher transient currents in the V
during reset. Special care should be taken to minimize the noise levels on the PLL supply pins.
4.7
MOTOROLA
Semiconductor Equipment and Materials International
805 East Middlefield Rd.
Mountain View, CA 94043
MIL-SPEC and EIA/JESD (JEDEC) Specifications
(Available from Global Engineering Documents)
JEDEC Specifications
1. C.E. Triplett and B. Joiner, “An Experimental Characterization of a 272 PBGA Within an
2. B. Joiner and V. Adams, “Measurement and Simulation of Junction to Board Thermal Resistance
CC
T
P
Automotive Engine Controller Module,” Proceedings of SemiTherm, San Diego, 1998, pp. 47–54.
and Its Application in Thermal Modeling,” Proceedings of SemiTherm, San Diego, 1999, pp.
212–220.
D
T
JT
pin should be provided with a low-impedance path to the board’s power supply. Each ground pin
= thermocouple temperature on top of package
= power dissipation in package
Experimental Determination
Layout Practices
References
= thermal characterization parameter
T
J
= T
MPC8272 PowerQUICC II™ Family Hardware Specifications
PRELIMINARY—SUBJECT TO CHANGE WITHOUT NOTICE
T
+ (
Freescale Semiconductor, Inc.
For More Information On This Product,
JT
CC
CC
power supply should be bypassed to ground using at least four 0.1 µF
and GND circuits. Pull up all unused inputs or signals that will be inputs
P
D
Go to: www.freescale.com
JT
)
) can be used to determine the junction temperature with a
CC
and ground should be kept to less than half an inch
CC
and GND planes is recommended.
Thermal Characteristics
[phone]
800-854-7179 or
303-397-7956
http://www.jedec.org
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