FB

SW

RTN

DRIVER

BST

SS

LM25010

7V BIAS

REGULATOR

+

-

SGND

ISEN

C6

GND

LEVEL

SHIFT

LOGIC

Driver

Gate Drive

UVLO

START

260 ns

OFF TIMER

OVER-VOLTAGE

COMPARATOR

GND

BYPASS

SWITCH

Shutdown

Input

THERMAL

SHUTDOWN

ON TIMER

COMPLETE

START

C5

C1

RON

Input

6V-42V

C3

C4

L1

D1

C2

R2

R1

R3

RSENSE

50 m:

CURRENT LIMIT

COMPARATOR

REGULATION

COMPARATOR

2.9V

VIN

Q1

RCL

(optional)

VOUT

62.5 mV

11.5 PA

2.5V

Q2

SD

RON

COMPLETE

VCC

UVL

VIN SENSE

VCC

VIN

RON/SD

0.7V

Copyright © 2016, Texas Instruments Incorporated

8

LM25010, LM25010-Q1

SNVS419E – DECEMBER 2005 – REVISED MAY 2016

www.ti.com

Product Folder Links: LM25010 LM25010-Q1

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Copyright © 2005–2016, Texas Instruments Incorporated

7 Detailed Description

7.1 Overview

The LM25010 step-down switching regulator features all the functions needed to implement a low cost, efficient

buck DC-DC converter capable of supplying in excess of 1 A to the load. This high voltage regulator integrates

an N-Channel buck switch, with an easy to implement constant ON-time controller. It is available in the thermally

enhanced WSON and HTSSOP packages. The regulator compares the feedback voltage to a 2.5-V reference to

control the buck switch, and provides a switch ON-time which varies inversely with VIN. This feature results in the

operating frequency remaining relatively constant with load and input voltage variations. The switching frequency

can range from less than 100 kHz to 1 MHz. The regulator requires no loop compensation resulting in very fast

load transient response. The valley current limit circuit holds the buck switch off until the free-wheeling inductor

current falls below the current limit threshold, nominally set at 1.25 A.

The LM25010 can be applied in numerous applications to efficiently step-down higher DC voltages. Features

include: thermal shutdown, VCC undervoltage lockout, gate drive undervoltage lockout, and maximum duty cycle

limit.

7.2 Functional Block Diagram

7.3 Feature Description

7.3.1 Control Circuit Overview

The LM25010 employs a control scheme based on a comparator and a one-shot ON timer, with the output

voltage feedback (FB) compared to an internal reference (2.5 V). If the FB voltage is below the reference the

buck switch is turned on for a time period determined by the input voltage and a programming resistor (RON).

Following the ON-time the switch remains off for a fixed 260-ns OFF-time, or until the FB voltage falls below the

reference, whichever is longer. The buck switch then turns on for another ON-time period. Referring to the

Functional Block Diagram, the output voltage is set by R1 and R2. The regulated output voltage is calculated

with Equation 1.

VOUT = 2.5 V × (R1 + R2) / R2

(1)