Typical Application Circuits

Layout Information

LAYOUT CONSIDERATIONS

The LM3351’s high switching frequency (200 kHz) makes a good layout important.

Figure 3 illustrates a typical layout. It is im-

portant to keep the distance short between the four capacitors and the IC. Wide traces and grounding are also recommended.

These steps will minimize trace inductance and high frequency ringing. Of the four capacitors, C

value of di/dt. It is therefore most important to keep them close to the IC. The ground lead that C

be kept wide and short.

The location of the diode (D1) used in the step-up configuration is not critical. This diode is only used during the initial turn on of

the IC. D1 is not needed in step-down applications.

DS100146-12

FIGURE 1. Step-Up Converter

DS100146-13

FIGURE 2. Step-Down Converter

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