Max Duty

Cycle Limit

OSC

DC

LIMIT

SET

+

+

-

+

PWM

Comp

RESET

FET

Driver

BUCK

DRIVE

+

-

Error

Amp

FB

Bandgap

Soft

Start

Thermal

Shutdown

TSD

SHDN

Inductor

Current

Measurement

CB

SW

GND

UVLO

Comp

BG

UVLO

Voltage

Regulator

VIN

Copyright © 2016, Texas Instruments Incorporated

9

LM2840-Q1, LM2841-Q1, LM2842-Q1

www.ti.com

SNVSBE5 – APRIL 2019

Product Folder Links: LM2840-Q1 LM2841-Q1 LM2842-Q1

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Copyright © 2019, Texas Instruments Incorporated

7 Detailed Description

7.1 Overview

The LM284x-Q1 SIMPLE SWITCHER® regulators are easy-to-use, non-synchronous, step-down DC/DC

converters with a wide input voltage range up to 42 V. The devices are capable of delivering up to 100

‑mA, 300-

mA, or 600-mA DC load current with excellent line and load regulation. These devices are available in fixed

frequency of 550 kHz and 1.25 MHz. The family requires few external components, and the pin arrangement was

designed for simple, optimum PCB layout.

7.2 Functional Block Diagram

7.3 Feature Description

7.3.1 Protection

The LM284x-Q1 have dedicated protection circuitry running during normal operation to protect the IC. The

thermal shutdown circuitry turns off the power device when the die temperature reaches excessive levels. The

UVLO comparator protects the power device during supply power start-up and shutdown to prevent operation at

voltages less than the minimum input voltage. A gate drive (CB) undervoltage lockout is included to ensure that

there is enough gate drive voltage to drive the MOSFET before the device tries to start switching. The LM284x-

Q1 also feature a shutdown mode decreasing the supply current to approximately 16 µA.