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LM2670

SNVS036K – APRIL 2000 – REVISED JUNE 2016

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7 Detailed Description

7.1 Overview

The LM2670 provides all of the active functions required for a step-down (buck) switching regulator. The internal

power switch is a DMOS power MOSFET to provide power supply designs with high current capability, up to 3 A,

and highly efficient operation.

The design support WEBENCH, can also be used to provide instant component selection, circuit performance

calculations for evaluation, a bill of materials component list and a circuit schematic for LM2670.

7.2 Functional Block Diagram

* Active Inductor Patent Number 5,514,947

† Active Capacitor Patent Number 5,382,918

7.3 Feature Description

7.3.1 Switch Output

This is the output of a power MOSFET switch connected directly to the input voltage. The switch provides energy

to an inductor, an output capacitor, and the load circuitry under control of an internal pulse-width-modulator

(PWM). The PWM controller is internally clocked by a fixed 260-kHz oscillator. In a standard step-down

application the duty cycle (Time ON/Time OFF) of the power switch is proportional to the ratio of the power

ground by the voltage drop of the external Schottky diode (switch OFF).