LTM8027

10

8027f

BLOCK DIAGRAM

OPERATION

The LTM8027 is a standalone nonisolated step-down

switching DC/DC power supply with an input voltage

range of 4.5V to 60V that can deliver up to 4A of output

current. This module provides a precisely regulated output

voltage up to 24V, programmable via one external resistor.

Given that the LTM8027 is a step-down converter, make

sure that the input voltage is high enough to support the

desired output voltage and load current. A simplified block

diagram is given above. The LTM8027 contains a current

mode controller, power switching element, power induc-

tor, power MOSFETs and a modest amount of input and

output capacitance.

The LTM8027 is a fixed frequency PWM regulator. The

switching frequency is set by simply connecting the ap-

propriate resistor from the RT pin to GND.

A linear regulator provides internal power (shown as

if the BIAS1and BIAS2 pins are connected to an external

voltage higher than 8.5V, bias power will be drawn from

the external source (typically the regulated output voltage).

This improves efficiency. The RUN pin is used to enable

or place the LTM8027 in shutdown, disconnecting the

output and reducing the input current to less than 10μA.

8027 BD

6.8μH

RUN

2.2μF

CURRENT

MODE

CONTROLLER

INTERNAL

CONNECTION

SS

SYNC

AUX

BIAS1

BIAS2

GND

ADJ

INTERNAL

LINEAR

REGULATOR

4.7pF

499k