Product details

Vin (Min) (V) 3.5 Vin (Max) (V) 40 Vout (Min) (V) 1.23 Vout (Max) (V) 15 Switch current limit (Typ) (A) 3 Regulated outputs (#) 1 Switching frequency (Min) (kHz) 52 Switching frequency (Max) (kHz) 52 Iq (Typ) (mA) 10 Features UVLO Fixed Duty cycle (Max) (%) 95 Operating temperature range (C) -40 to 125 Rating Catalog
Vin (Min) (V) 3.5 Vin (Max) (V) 40 Vout (Min) (V) 1.23 Vout (Max) (V) 15 Switch current limit (Typ) (A) 3 Regulated outputs (#) 1 Switching frequency (Min) (kHz) 52 Switching frequency (Max) (kHz) 52 Iq (Typ) (mA) 10 Features UVLO Fixed Duty cycle (Max) (%) 95 Operating temperature range (C) -40 to 125 Rating Catalog
TO-220 (KC) 5 86 mm² 10.2 x 8.7 TO-220 (NDH) 5 86 mm² 10.16 x 8.47 TO-263 (KTT) 5 155 mm² 10.16 x 15.24
  • Requires Few External Components
  • NPN Output Switches 3.0A, can Stand off 65V
  • Wide Input Voltage Range: 3.5V to 40V
  • Current-mode Operation for Improved Transient Response, Line Regulation, and Current Limit
  • 52 kHz Internal Oscillator
  • Soft-start Function Reduces In-rush Current During Start-up
  • Output Switch Protected by Current Limit, Under-voltage Lockout, and Thermal Shutdown

All trademarks are the property of their respective owners.

  • Requires Few External Components
  • NPN Output Switches 3.0A, can Stand off 65V
  • Wide Input Voltage Range: 3.5V to 40V
  • Current-mode Operation for Improved Transient Response, Line Regulation, and Current Limit
  • 52 kHz Internal Oscillator
  • Soft-start Function Reduces In-rush Current During Start-up
  • Output Switch Protected by Current Limit, Under-voltage Lockout, and Thermal Shutdown

All trademarks are the property of their respective owners.

The LM1577/LM2577 are monolithic integrated circuits that provide all of the power and control functions for step-up (boost), flyback, and forward converter switching regulators. The device is available in three different output voltage versions: 12V, 15V, and adjustable.

Requiring a minimum number of external components, these regulators are cost effective, and simple to use. Listed in this data sheet are a family of standard inductors and flyback transformers designed to work with these switching regulators.

Included on the chip is a 3.0A NPN switch and its associated protection circuitry, consisting of current and thermal limiting, and undervoltage lockout. Other features include a 52 kHz fixed-frequency oscillator that requires no external components, a soft start mode to reduce in-rush current during start-up, and current mode control for improved rejection of input voltage and output load transients.

The LM1577/LM2577 are monolithic integrated circuits that provide all of the power and control functions for step-up (boost), flyback, and forward converter switching regulators. The device is available in three different output voltage versions: 12V, 15V, and adjustable.

Requiring a minimum number of external components, these regulators are cost effective, and simple to use. Listed in this data sheet are a family of standard inductors and flyback transformers designed to work with these switching regulators.

Included on the chip is a 3.0A NPN switch and its associated protection circuitry, consisting of current and thermal limiting, and undervoltage lockout. Other features include a 52 kHz fixed-frequency oscillator that requires no external components, a soft start mode to reduce in-rush current during start-up, and current mode control for improved rejection of input voltage and output load transients.

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Technical documentation

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Type Title Date
* Data sheet LM1577/LM2577 SIMPLE SWITCHER Step-Up Voltage Regulator datasheet (Rev. D) 03 Apr 2013
Application note Switching regulator fundamentals (Rev. C) 05 Feb 2019
Application note Semiconductor and IC Package Thermal Metrics (Rev. C) 19 Apr 2016
Application note Working With Boost Converters 15 Jun 2015
Application note Basic Calculation of a Boost Converter's Power Stage (Rev. C) 08 Jan 2014
Application note AN-2162 Simple Success With Conducted EMI From DC-DC Converters (Rev. C) 24 Apr 2013
Application note AN-1149 Layout Guidelines for Switching Power Supplies (Rev. C) 23 Apr 2013
Application note AN-1229 SIMPLE SWITCHER PCB Layout Guidelines (Rev. C) 23 Apr 2013
Application note AN-1520 A Guide to Board Layout for Best Thermal Resistance for Exposed Packages (Rev. B) 23 Apr 2013
Application note AN-1566 Techniques for Thermal Analysis of Switching Power Supply Designs (Rev. A) 23 Apr 2013
Application note AN-1889 How to Measure the Loop Transfer Function of Power Supplies (Rev. A) 23 Apr 2013
Application note AN-2155 Layout Tips for EMI Reduction in DC/ DC Converters (Rev. A) 23 Apr 2013
Application note AN-776 20-W SIMPLE SWITCHER Forward Converter (Rev. A) 23 Apr 2013
Application note AN-777 LM2577 Three Output, Isolated Flyback Regulator (Rev. B) 23 Apr 2013
Application note Negative Buck Switching Regulator (using LM258x) 21 Mar 2007
Application note Input and Output Capacitor Selection 19 Sep 2005
More literature SEM1600 Topic 4: Constructing Your Power Supply – Layout Considerations 12 Jul 2005
Application note AN-643 EMI/RFI Board Design (Rev. B) 03 May 2004
Application note Understanding Boost Power Stages In Switchmode Power Supplies 04 Mar 1999

Design & development

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Simulation tool

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FLYBUCK-FLYBACK-DESIGN-CALC — Fly-Buck and Flyback Topology Selector

This tool helps a power supply engineer to select the right isolated DC-DC topology based on the specifications. Depending on the topology chosen, the calculator also recommends the right IC for the design.
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SWITCHERSMADESIMPLE-SW — Switchers Made Simple

Note: The Switchers Made Simple design computations have been incorporated into Texas Instruments' award winning WEBENCH Power Designer Online Design Tool. Please use TI's WEBENCH Power Designer online tools for new designs. The WEBENCH Design Tool also includes:
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DDPAK/TO-263 (KTT) 5 View options
TO-220 (KC) 5 View options
TO-220 (NDH) 5 View options

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