PCB layout guidelines

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PCB layout guidelines

A recommended printed circuit board (PCB) layout for the ST1S03 inverting regulator is

shown in Figure 9. It is very important to place the input capacitor as close as possible to the

input pin of the regulator. In order to achieve the best performance, special care must be

taken to ensure proper grounding. A good practice is to always use a separate ground

plane, or at a minimum a single point ground structure.

High switching currents may cause voltage drops in the PCB metal trace, and long metal

traces and component leads cause unwanted parasitic inductance as well, especially at

switching frequencies of 1.5 MHz. This parasitic inductance is very often the main source of

EMI problems and high voltage spikes at input and output lines. Therefore, place the

inductor, freewheeling diode, and especially the input capacitor as close as possible to the

device. Use big lines for the metal traces to these components. Wire the feedback circuit

away from the inductor to avoid flux intersection. The use of a ground ring guard is

recommended. Use shielded cores for better EMI performance. Capacitors with low ESR

are recommended the for inputs and outputs.

Figure 9.

PCB layout - top side