FB

SW

L1

RFB2

LM34922

BST

CBST

D1

CS

RT

VIN

6V to 28V

Input

CIN

SS

CSS

RT

SGND

PGD

CSG

RS

RPGD

VPGD

COUT

RFB1

VOUT

Power

Good

LM34922

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SNVS813A – JUNE 2012 – REVISED MARCH 2013

LM34922 28V, 2A Constant On-Time Switching Regulator with Adjustable Current Limit

Check for Samples: LM34922

1

FEATURES

•

Thermal Shutdown

•

Precision 2% Feedback Reference

2

•

Input Operating Voltage Range: 6V to 28V

•

Absolute Maximum Input Rating: 30V

DESCRIPTION

•

Integrated 2A N-Channel Buck Switch

The

LM34922

Constant

On-time

Step-Down

•

Adjustable Current Limit Allows for Smaller

Switching Regulator features all the functions needed

Inductor

to implement a low cost, efficient, buck bias regulator

capable of supplying up to 2A of load current. This

•

Adjustable Output Voltage from 2.51V

voltage regulator contains an N-Channel Buck switch,

•

Minimum Ripple Voltage at VOUT

a startup regulator, current limit detection, and

•

Power Good Output

internal

ripple

control.

The

constant

on-time

regulation principle requires no loop compensation,

•

Switching Frequency Adjustable to 1MHz

results in fast load transient response, and simplifies

•

COT Topology Features:

circuit

implementation.

The

operating

frequency

–

Switching Frequency Remains Nearly

remains constant with line and load. The adjustable

Constant with Load Current and Input

valley current limit detection results in a smooth

Voltage Variations

transition from constant voltage to constant current

mode when current limit is reached, without the use

–

Ultra-Fast Transient Response

of current limit foldback. The PGD output indicates

–

No Loop Compensation Required

the output voltage has increased to within 5% of the

–

Stable Operation with Ceramic Output

expected

regulation

value.

Additional

features

Capacitors

include: Low output ripple, VIN under-voltage lock-

out, adjustable soft-start timing, thermal shutdown,

–

Allows for Smaller Output Capacitor and

gate drive pre-charge, gate drive under-voltage lock-

Current Sense Resistor

out, and maximum duty cycle limit.

•

Adjustable Soft-Start Timing

Typical Application, Basic Step-Down Regulator

1

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Texas Instruments semiconductor products and disclaimers thereto appears at the end of this data sheet.

2

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PRODUCTION DATA information is current as of publication date.

Copyright © 2012–2013, Texas Instruments Incorporated

Products conform to specifications per the terms of the Texas

Instruments standard warranty. Production processing does not

necessarily include testing of all parameters.