LM2596: SIMPLE SWITCHER® Power Converter 150-kHz 3-A Step-Down Voltage Regulator

LM2596:  SIMPLE SWITCHER® Power Converter 150-kHz 3-A Step-Down Voltage Regulator

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 over temperature shutdown for complete protection under fault conditions.

 

Features

  • 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 Conditions
  • 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

Applications

  • Simple High-Efficiency Step-Down (Buck) Regulator
  • On-Card Switching Regulators
  • Positive-to-Negative Converter 

 

Thermal Considerations

The LM2596 is available in two packages: a 7-pin TO-220 (T) and a 7-pin surface mount TO-263 (S).
The TO-220 package requires a heat sink under most conditions. The size of the heat sink depends on the input voltage, the output voltage, the load current and the ambient temperature. the LM2596T junction temperature rises above ambient temperature for a 3-A load and different input and output voltages. The data for these curves was taken with the LM2596T (TO-220 package) operating as a buck switching regulator in an ambient temperature of 25°C (still air). These temperature rise numbers are all approximate and there are many factors that can affect these temperatures. Higher ambient temperatures require more heat sinking.
The TO-263 surface mount package tab is designed to be soldered to the copper on a printed-circuit board (PCB). The copper and the board are the heat sink for this package and the other heat producing components, such as the catch diode and inductor. The PCB copper area that the package is soldered to must be at least 0.4 in2, and ideally must have 2 or more square inches of 2-oz. (0.0028 in.) copper. Additional copper area improves the thermal characteristics, but with copper areas greater than approximately 6 in2, only small improvements in heat dissipation are realized. If further thermal improvements are required, TI recommends double-sided, multilayer PCB with large copper areas and airflow.
Straight Leads 5-Lead TO-220 Package LM2575T-XX or LM2575HVT-XX
DDPAK/TO-263 Package 5-Lead Surface-Mount Package LM2575S-XX or LM2575HVS-XX

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