MPC8347ECVRADDB datasheet(92/99 Pages) FREESCALE

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MPC8347EA PowerQUICC II Pro Integrated Host Processor Hardware Specifications, Rev. 12

Freescale Semiconductor

System Design Information

capacitive loads. This noise must be prevented from reaching other components in the MPC8347EA

system, and the device itself requires a clean, tightly regulated source of power. Therefore, the system

designer should place at least one decoupling capacitor at each VDD, OVDD, GVDD, and LVDD pin of the

device. These capacitors should receive their power from separate VDD, OVDD, GVDD, LVDD, and GND

power planes in the PCB, with short traces to minimize inductance. Capacitors can be placed directly under

the device using a standard escape pattern. Others can 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, distribute several bulk storage capacitors 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. They should also

be connected to the power and ground planes through two vias to minimize inductance. Suggested bulk

capacitors are 100–330 µF (AVX TPS tantalum or Sanyo OSCON).

21.4

Connection Recommendations

To ensure reliable operation, 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 MPC8347EA.

21.5

Output Buffer DC Impedance

The MPC8347EA 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 44). The

output impedance is the average of two components, the resistances of the pull-up and pull-down devices.

When data is held high, SW1 is closed (SW2 is open) and RP is trimmed until the voltage at the pad equals

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