FB

LM25085A

PGATE

ISEN

GND

VCC

ADJ

4.5V to 42V

Input

GND

SHUTDOWN

Q1

D1

L1

Cff

GND

VIN

RT

LM25085A

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SNVS601A – JANUARY 2009 – REVISED MARCH 2009

LM25085A 42V Constant On-Time PFET Buck Switching Controller with 0.9V Reference

Check for Samples: LM25085A

1

FEATURES

and load variations

•

Adjustable output voltage from 0.9V

2

•

Wide 4.5V to 42V input voltage range

•

Precision ±2% feedback reference

•

current sense resistor

•

Capable of 100% duty cycle operation

•

Programmable switching frequency to 1MHz

•

Internal soft-start timer

•

No loop compensation required

•

Integrated high voltage bias regulator

•

Ultra-Fast transient response

•

Thermal shutdown

•

Nearly constant operating frequency with line

DESCRIPTION

The LM25085A is a functional variant of the LM25085 COT PFET Buck Switching Controller. The functional

differences of the LM25085A are: The feedback reference voltage is 0.9V, the forced off-time after current limit

detection is longer, and the soft-start time is shorter (1.8 ms).

The LM25085A is a high efficiency PFET switching regulator controller that can be used to quickly and easily

develop a small, efficient buck regulator for a wide range of applications. This high voltage controller contains a

PFET gate driver and a high voltage bias regulator which operates over a wide 4.5V to 42V input range. The

constant on-time regulation principle requires no loop compensation, simplifies circuit implementation, and results

in ultra-fast load transient response. The operating frequency remains nearly constant with line and load

variations due to the inverse relationship between the input voltage and the on-time. The PFET architecture

resistor can be used to sense current for over-current detection.

Package

•

MSOP-8EP

•

MSOP-8

•

LLP-8 (3 mm x 3 mm)

Typical Application, Basic Step Down Controller

1

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

2

All trademarks are the property of their respective owners.

PRODUCTION DATA information is current as of publication date.

Copyright © 2009, 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.