mpc7450 Freescale Semiconductor, Inc, mpc7450 Datasheet - Page 39

• Manufacturer Part Number: mpc7450
• Description: Mpc7450 Risc Microprocessor
• Manufacturer: Freescale Semiconductor, Inc

diodes (see Figure 21) control the maximum potential difference between the external bus and core power
supplies on power-up and the 1N5820 diodes regulate the maximum potential difference on power-down.
1.9.4
Due to the MPC7450 dynamic power management feature, large address and data buses, and high operating
frequencies, the MPC7450 can generate transient power surges and high frequency noise in its power
supply, especially while driving large capacitive loads. This noise must be prevented from reaching other
components in the MPC7450 system, and the MPC7450 itself requires a clean, tightly regulated source of
power. Therefore, it is recommended that the system designer place at least one decoupling capacitor at each
V
receive their power from separate V
traces to minimize inductance.
These capacitors should have a value of 0.01 µF or 0.1 µF. Only ceramic surface mount technology (SMT)
capacitors should be used to minimize lead inductance, preferably 0508 or 0603 orientations where
connections are made along the length of the part. Consistent with the recommendations of Dr. Howard
Johnson in High Speed Digital Design: A Handbook of Black Magic (Prentice Hall, 1993) and contrary to
previous recommendations for decoupling Motorola microprocessors, multiple small capacitors of equal
value are recommended over using multiple values of capacitance.
In addition, it is recommended that there be several bulk storage capacitors distributed around the PCB,
feeding the V
bulk capacitors should have a low equivalent series resistance (ESR) rating to ensure the quick response
time necessary. They should also be connected to the power and ground planes through two vias to minimize
inductance. Suggested bulk capacitors: 100–330 µF (AVX TPS tantalum or Sanyo OSCON).
1.9.5
To ensure reliable operation, it is highly recommended to connect unused inputs to an appropriate signal
level. Unused active low inputs should be tied to OV
GND. All NC (no-connect) signals must remain unconnected.
Power and ground connections must be made to all external V
MPC7450. If the L3 interface is not used, GV
L3VSEL should be connected to BVSEL.
MOTOROLA
DD
, OV
DD
Decoupling Recommendations
Connection Recommendations
, and GV
DD
, GV
DD
DD
MPC7450 RISC Microprocessor Hardware Specifications
, and OV
pin of the MPC7450. It is also recommended that these decoupling capacitors
Freescale Semiconductor, Inc.
Figure 21. Example Voltage Sequencing Circuit
2.5 V
For More Information On This Product,
DD
planes, to enable quick recharging of the smaller chip capacitors. These
DD
, OV
Go to: www.freescale.com
DD
30BF10
/GV
1N5820
DD
DD
should be connected to the OV
DD
, and GND power planes in the PCB, utilizing short
30BF10
. Unused active high inputs should be connected to
1N5820
DD
, OV
DD
1.6 V
, GV
System Design Information
DD
, and GND pins in the
DD
power phase, and
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