DSP56004ROM datasheet(77/82 Pages) FREESCALE

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Design Considerations

Electrical Design Considerations

MOTOROLA

DSP56004/D, Rev. 3

4-3

ELECTRICAL DESIGN CONSIDERATIONS

Use the following list of recommendations to assure correct DSP operation:

•

Provide a low-impedance path from the board power supply to each VCC

pin on the DSP, and from the board ground to each GND pin.

•

Use at least four 0.01–0.1

µF bypass capacitors positioned as close as

possible to the four sides of the package to connect the VCC power source

to GND.

•

Ensure that capacitor leads and associated printed circuit traces that

connect to the chip VCC and GND pins are less than 0.5 in per capacitor

lead.

•

Use at least a four-layer Printed Circuit Board (PCB) with two inner layers

for VCC and GND.

•

Because the DSP output signals have fast rise and fall times, PCB trace

lengths should be minimal. This recommendation particularly applies to

the address and data buses as well as the IRQA, IRQB, and NMI pins.

Maximum Printed Circuit Board (PCB) trace lengths on the order of

6 inches are recommended.

•

Consider all device loads as well as parasitic capacitance due to PCB

traces when calculating capacitance. This is especially critical in systems

with higher capacitive loads that could create higher transient currents in

the VCC and GND circuits.

•

All inputs must be terminated (i.e., not allowed to float) using CMOS

levels, except as noted in Section 1.

•

Take special care to minimize noise levels on the VCCP and GNDP pins.

•

If multiple DSP56004 devices are on the same board, check for cross-talk

or excessive spikes on the supplies due to synchronous operation of the

devices.

CAUTION

This device contains protective circuitry to guard against

damage due to high static voltage or electrical fields.

However,

normal

precautions

are

advised

avoid

application of any voltages higher than maximum rated

voltages to this high-impedance circuit. Reliability of

operation is enhanced if unused inputs are tied to an

appropriate logic voltage level (e.g., either GND or VCC).

Freescale Semiconductor, Inc.

For More Information On This Product,

Go to: www.freescale.com

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