MSC8113 Tri-Core Digital Signal Processor Data Sheet, Rev. 0

Hardware Design Considerations

Freescale Semiconductor

38

3

Hardware Design Considerations

The following sections discuss areas to consider when the MSC8113 device is designed into a system.

3.1

Start-up Sequencing Recommendations

Use the following guidelines for start-up and power-down sequences:

required minimum power levels. This can be implemented via weak pull-down resistors.

•

CLKIN

•

Note:

This recommended power sequencing for the MSC8113 is different from the MSC8102.

power-up. Some designs require pull-up voltages applied to selected input lines during power-up for configuration purposes.

This is an acceptable exception to the rule. However, each such input can draw up to 80 mA per input pin per device in the

system during start-up.

3.2

Power Supply Design Considerations

When implementing a new design, use the guidelines described in the MSC8113 Design Checklist (AN3374 for optimal system

performance. MSC8122 and MSC8126 Power Circuit Design Recommendations and Examples (AN2937) provides detailed

design information.

Figure 32 shows the recommended power decoupling circuit for the core power supply. The voltage regulator and the

decoupling capacitors should supply the required device current without any drop in voltage on the device pins. The voltage on

the package pins should not drop below the minimum specified voltage level even for a very short spikes. This can be achieved

by using the following guidelines:

•

For the core supply, use a voltage regulator rated at 1.1 V with nominal rating of at least 3 A. This rating does not

reflect actual average current draw, but is recommended because it resists changes imposed by transient spikes and has

better voltage recovery time than supplies with lower current ratings.

•

Decouple the supply using low-ESR capacitors mounted as close as possible to the socket. Figure 32 shows three

capacitors in parallel to reduce the resistance. Three capacitors is a recommended minimum number. If possible, mount

at least one of the capacitors directly below the MSC8113 device.

Figure 32. Core Power Supply Decoupling

+

-

Power supply

or

Voltage Regulator

High frequency capacitors

(very low ESR and ESL)

Bulk/Tantalum capacitors

with low ESR and ESL

MSC8113

Maximum IR drop

of 15 mV at 1 A

Note: Use at least three capacitors.

One 0.01 µF capacitor

for every 3 core supply

pads.

1.1 V

Each capacitor must be at least 150

μF.