ICS1531 datasheet(58/76 Pages) ICST

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ICS1531 Rev N 12/1/99

December, 1999

Chapter 8

Layout and Power Considerations

ICS1531 Data Sheet - Preliminary

Chapter 8

Layout and Power Considerations

8.1

Layout Considerations

8.1.1

General Guidelines for Printed Circuit Board Layout

To lay out a printed circuit board that uses the ICS1531, see Figure 8-1 and use the following general

guidelines.

• Use a printed circuit board with at least the following four planes:

– One power plane

– One ground plane. (No special cutouts required.)

– Two signal planes

• Power supply voltages:

– Provide all supply voltages from a common source.

– Ensure that all supply voltages ramp together.

– Bypass each power supply pin with a 0.1-

µF capacitor.

• When using capacitors for filtering or decoupling, use either tantalum or ceramic capacitors with good

high-frequency characteristics. (Do not use electrolytic capacitors.) Place the capacitors as close as

possible to the ICS1531 pins that are being filtered or decoupled.

• Trace widths:

– Use nominal trace widths of approximately 0.020 to 0.025 cm.

– Use a maximum trace width of approximately 0.076 cm.

• As Figure 8-1 indicates, connect the appropriate VDDx and VSSx pins to the appropriate plane, using

multiple surface-etched vias.

• Ensure that the area of the printed circuit board where the ICS1531 is placed is free of contaminants.

(Flux and other board-surface debris can degrade the performance of the external loop filter.)

Figure 8-1.

General Decoupling Circuit for ICS1531

0.1

µF0.1 µF

µF

Multiple vias

ICS1531

VDDx

VSSx

Multiple vias

VCC

Width from ~

0.025 to

0.076 cm

1.27 cm max

2.54 cm max

Ferrite bead

ICS1531 Datasheet(PDF) 58 Page - Integrated Circuit Systems

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