LM3478MASLASHNOPB datasheet(17/43 Pages) TI2

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LM3478

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SNVS085X – JULY 2000 – REVISED DECEMBER 2017

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Typical Applications (continued)

First Cycle Operation

Second Cycle of Operation

Figure 28. Simplified Boost Converter

8.2.1.1 Design Requirements

To properly size the components for the application, the designer needs the following parameters: input voltage

range, output voltage, output current range, and required switching frequency. These four main parameters affect

the choices of component available to achieve a proper system behavior.

For the power supply, the input impedance of the supply rail should be low enough that the input current

transient does not drop below the UVLO value. The factors determining the choice of inductor used should be

the average inductor current, and the inductor current ripple. If the switching frequency is set high, the converter

can be operated with very small inductor values. The maximum current that can be delivered to the load is set by

the sense resistor, RSEN. Current limit occurs when the voltage generated across the sense resistor equals the

current sense threshold voltage, VSENSE. Also, a resistor RSL adds additional slope compensation, if required.

The following sections describe the design requirements for a typical LM3478 boost application.

8.2.1.2 Detailed Design Procedure

8.2.1.2.1

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LM3478MA/NOPB Datasheet(PDF) 17 Page - Texas Instruments