OPTIMIZING LAYOUT

Optimizing a PC board layout involves to observe

the following rules which in general can avoid ap-

plication problems associated with ground loops

and anomalous recirculation currents. The elec-

trolytic capacitor for the power supply must be

kept as close to the IC as possible. It is important

that power grounds are close to each other on a

wide enough. Copper side also, it is important to

separate on the board the logic ground and the

power ground in such a way that the ground

traces for the logic signals and references do not

cross the ground traces for the power signals.

Logic ground and power ground must meet at

one point on the board (startpoint grounding) far

enough away from where the power ground

traces terminate to ground (sense resistors and

recirculation diodes). This is to avoid anomalous

interface with the logic signals. It is generally a

good idea to connect a non inductive capacitor

(typically 100nF) between the pins VS and GND.

In other cases it may be necessary to also place

a by-pass capacitor between the pins Vref and

GND.

Figure 1: Voice Coil Motor Control Circuit

L6242

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