LTM8022MPV datasheet(7/20 Pages) LINER

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LTM8022

8022fb

OPERATION

The LTM8022 is a standalone non-isolated step-down

switching DC/DC power supply. It can deliver up to 1A of

DC output current with only bulk external input and output

capacitors. This module provides a precisely regulated

output voltage programmable via one external resistor

from 0.8VDC to 10VDC. The input voltage range is 3.6V

to 36V. Given that the LTM8022 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 shown above.

The LTM8022 contains a current mode controller, power

switching element, power inductor, power Schottky diode

and a modest amount of input and output capacitance.

The LTM8022 is a ﬁxed frequency PWM regulator. The

switching frequency is set by simply connecting the ap-

propriate value resistor from the RT pin to GND.

An internal regulator provides power to the control cir-

cuitry. The bias regulator normally draws power from the

VIN pin, but if the BIAS pin is connected to an external

voltage higher than 2.4V, bias power will be drawn from

the external source (typically the regulated output voltage).

This improves efﬁciency. The RUN/SS pin is used to place

the LTM8022 in shutdown, disconnecting the output and

reducing the input current to less than 1μA.

To further optimize efﬁciency, the LTM8022 automatically

switches to Burst Mode operation in light load situations.

Between bursts, all circuitry associated with controlling the

output switch is shut down reducing the input supply cur-

rent to 50μA in a typical application. The oscillator reduces

the LTM8022’s operating frequency when the voltage at the

ADJ pin is low. This frequency foldback helps to control

the output current during start-up and overload.

The LTM8022 contains a power good comparator which

trips when the ADJ pin is at 92% of its regulated value.

The PG output is an open-collector transistor that is off

when the output is in regulation, allowing an external

resistor to pull the PG pin high. Power good is valid when

the LTM8022 is enabled and VIN is above 3.6V.

BLOCK DIAGRAM

VIN

8022 BD

BIAS

AUX

CURRENT MODE

CONTROLLER

VOUT

10μF

4.7pF

4.7μH

0.1μF

499k

SYNC

RUN/SS

ADJ

GND

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