Detailed Description

OPERATING PRINCIPLE

The LM2621 is designed to provide step-up DC-DC voltage

regulation in battery-powered and low-input voltage sys-

tems. It combines a step-up switching regulator, N-channel

power MOSFET, built-in current limit, thermal limit, and volt-

age reference in a single 8-pin MSOP package . The switch-

ing DC-DC regulator boosts an input voltage between 1.2V

and 14V to a regulated output voltage between 1.24V and

14V. The LM2621 starts from a low 1.1V input and remains

operational down to 0.65V.

This device is optimized for use in cellular phones and other

applications requiring a small size, low profile, as well as low

quiescent current for maximum battery life during stand-by

and shutdown. A high-efficiency gated-oscillator topology of-

fers an output of up to 1A.

Additional features include a built-in peak switch current

limit, and thermal protection circuitry.

GATED OSCILLATOR CONTROL SCHEME

A unique gated oscillator control scheme enables the

LM2621 to have an ultra-low quiescent current and provides

a high efficiency over a wide load range. The switching fre-

quency of the internal oscillator is programmable using an

external resistor and can be set between 300 kHz and 2

MHz.

Peak Inductor Current vs

Load Current

DS100934-10

Maximum Load Current vs

Input Voltage

DS100934-11

DS100934-14

FIGURE 1. Functional Diagram

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