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ALQ07 DC-DC Converter Technical Reference Notes

DATE: Aug., 9, 2003

Extra care should be taken when long leads or traces are used to provide power to

the load. Long lead lengths increase the chance for noise to appear on the lines.

Under these conditions C1 can be added across the load, with a 0.1uF ceramic

capacitor C1 in parallel generally as shown in Figure ‘Output Ripple Filter for a

Distant Load’.

Decoupling

Noise on the power distribution system is not always created by the converter. High

speed analog or digital loads with dynamic power demands can cause noise to

cross the power inductor back onto the input lines. Noise can be reduced by

decoupling the load. In most cases, connecting a 10uF tantalum or ceramic

capacitor in parallel with a 0.1uF ceramic capacitor across the load will decouple it.

The capacitors should be connected as close to the load as possible.

Ground Loops

Ground loops occur when different circuits are given multiple paths to common or

earth ground, as shown in Figure ‘Ground Loops’. Multiple ground points can be

slightly different potential and cause current flow through the circuit from one point to

another. This can result in additional noise in all the circuits. To eliminate the

problem, circuits should be designed with a single ground connection as shown in

Figure ‘Single Point Ground’.