(ACTIVE) SIMPLE SWITCHER® 40V, 500mA Low Component Count Step-Down Regulator


Functional Diagram

Typical Application

Typical Performance


The LM2594xx series of regulators are monolithic integrated circuits that provide all the active functions for a step-down (buck) switching regulator, capable of driving a 0.5-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, and are packaged in a 8-pin PDIP and a 8-pin surface-mount SOIC package.

Requiring a minimum number of external components, these regulators are simple to use and feature internal frequency compensation, a fixed-frequency oscillator, and improved line and load regulation specifications.

The LM2594xx series operates at a switching frequency of 150-kHz, thus allowing smaller-sized filter components than what would be needed with lower-frequency switching regulators. Because of its high efficiency, the copper traces on the printed-circuit board are normally the only heat sinking needed.

A standard series of inductors (both through-hole and surface-mount types) are available from several different manufacturers optimized for use with the LM2594xx series. This feature greatly simplifies the design of switch-mode power supplies.

Other features include an ensured ±4% tolerance on output voltage under all conditions of input voltage and output load conditions, and ±15% on the oscillator frequency. External shutdown is included, featuring typically 85-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.

The LM2594HV is for applications requiring an input voltage up to 60 V.


  • 3.3-V, 5-V, 12-V, and Adjustable Output Versions
  • Adjustable Version Output Voltage Range: 1.2 V
    to 37 V (57 V for the HV Version), ±4% Maximum
    Over Line and Load Conditions
  • Available in 8-Pin Surface-Mount SOIC and 8-Pin
    PDIP Packages
  • Ensured 0.5-A Output Current
  • Input Voltage Range up to 60 V
  • Requires Only 4 External Components
  • 150-kHz Fixed-Frequency Internal Oscillator
  • TTL Shutdown Capability
  • Low Power Standby Mode, IQ Typically 85 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) 0.5    
Regulated outputs (#) 1    
Switching Frequency (Min) (kHz) 110    
Switching Frequency (Max) (kHz) 173    
Iq (Typ) (mA) 5    
Features Enable^Over Current Protection    
Control mode Voltage Mode    
Duty cycle (Max) (%) 100    
Operating temperature range (C) -40 to 125    
Rating Catalog    
Package Group PDIP|8^SOIC|8    
Type Converter    
Package size: mm2:W x L (PKG) See datasheet (PDIP)^8SOIC: 29 mm2: 6 x 4.9 (SOIC|8)    

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Application notes (17)

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