MPC8541CPXAJD View Datasheet(PDF) - Freescale Semiconductor
Part Name
Description
MFG CO.
MPC8541CPXAJD
Freescale Semiconductor
'MPC8541CPXAJD' PDF : 84 Pages View PDF
Figure 49 shows the PLL power supply filter circuit.
10 Ω
VDD
2.2 µF
2.2 µF
System Design Information
AVDD (or L2AVDD)
Low ESL Surface Mount Capacitors
GND
Figure 49. PLL Power Supply Filter Circuit
17.3 Decoupling Recommendations
Due to large address and data buses, and high operating frequencies, the MPC8541E 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 MPC8541E system, and the
MPC8541E 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 VDD, OVDD, GVDD, and LVDD pins
of the MPC8541E. These decoupling capacitors should receive their power from separate VDD, OVDD,
GVDD, LVDD, and GND power planes in the PCB, utilizing short traces to minimize inductance.
Capacitors may be placed directly under the device using a standard escape pattern. Others may surround
the part.
These capacitors should have a value of 0.01 or 0.1 µF. Only ceramic SMT (surface mount technology)
capacitors should be used to minimize lead inductance, preferably 0402 or 0603 sizes.
In addition, it is recommended that there be several bulk storage capacitors distributed around the PCB,
feeding the VDD, OVDD, GVDD, and LVDD planes, to enable quick recharging of the smaller chip
capacitors. These bulk capacitors should have a low ESR (equivalent series resistance) 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).
17.4 Connection Recommendations
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 OVDD, GVDD, or LVDD as required. Unused active high
inputs should be connected to GND. All NC (no-connect) signals must remain unconnected.
Power and ground connections must be made to all external VDD, GVDD, LVDD, OVDD, and GND pins of
the MPC8541E.
17.5 Output Buffer DC Impedance
The MPC8541E drivers are characterized over process, voltage, and temperature. For all buses, the driver
is a push-pull single-ended driver type (open drain for I2C).
To measure Z0 for the single-ended drivers, an external resistor is connected from the chip pad to OVDD
or GND. Then, the value of each resistor is varied until the pad voltage is OVDD/2 (see Figure 50). The
output impedance is the average of two components, the resistances of the pull-up and pull-down devices.
MPC8541E PowerQUICC™ III Integrated Communications Processor Hardware Specification, Rev. 4.2
Freescale Semiconductor
77
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