(ACTIVE) SIMPLE SWITCHER® 4.5V to 40V, 3A Low Component Count Step-Down Regulator


Functional Diagram

Typical Application

Typical Application


The LM2596 series of regulators are monolithic integrated circuits that provide all the active functions for a step-down (buck) switching regulator, capable of driving a 3-A load with excellent line and load regulation. These devices are available in fixed output voltages of 3.3 V, 5 V, 12 V, and an adjustable output version.

Requiring a minimum number of external components, these regulators are simple to use and include internal frequency compensation, and a fixed-frequency oscillator.

The LM2596 series operates at a switching frequency of 150 kHz, thus allowing smaller sized filter components than what would be required with lower frequency switching regulators. Available in a standard 7-pin TO-220 package with several different lead bend options, and a 7-pin TO-263 surface mount package.

A standard series of inductors are available from several different manufacturers optimized for use with the LM2596 series. This feature greatly simplifies the design of switch-mode power supplies.

Other features include a ±4% tolerance on output voltage under specified input voltage and output load conditions, and ±15% on the oscillator frequency. External shutdown is included, featuring typically 80 µA standby current. Self-protection features include a two stage frequency reducing current limit for the output switch and an overtemperature shutdown for complete protection under fault conditions.


  • 3.3-V, 5-V, 12-V, and Adjustable Output Versions
  • Adjustable Version Output Voltage Range: 1.2-V
    to 37-V ± 4% Maximum Over Line and Load
  • Available in TO-220 and TO-263 Packages
  • 3-A Output Load Current
  • Input Voltage Range Up to 40 V
  • Requires Only 4 External Components
  • Excellent Line and Load Regulation Specifications
  • 150-kHz Fixed-Frequency Internal Oscillator
  • TTL Shutdown Capability
  • Low Power Standby Mode, IQ, Typically 80 µA
  • High Efficiency
  • Uses Readily Available Standard Inductors
  • Thermal Shutdown and Current-Limit Protection


Vin (Min) (V) 4.5    
Vin (Max) (V) 40    
Vout (Min) (V) 3.3    
Vout (Max) (V) 37    
Iout (Max) (A) 3    
Regulated Outputs (#) 1    
Switching Frequency (Min) (kHz) 110    
Switching Frequency (Max) (kHz) 173    
Iq (Typ) (mA) 5    
Features Enable    
Control Mode Voltage Mode    
Duty Cycle (Max) (%) 100    
Operating Temperature Range (C) -40 to 125    
Rating Catalog    
Package Group DDPAK/TO-263|5^TO-220|5    
Type Converter    

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Application notes (17)

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