4A High Efficiency Switching Regulators

The LT1271 and LT1269 are monolithic high power switching regulators. Identical to the popular LT1070, except for switching frequency (LT1271 = 60kHz, LT1269 = 100kHz) and slightly lower switch current, they can be operated in all standard switching configurations including buck, boost, flyback and inverting. A high current, high efficiency switch is included on the die along with all oscillator, control and protection circuitry. Integration of all functions allows the LT1271/LT1269 to be built in a standard TO-220 power package. This makes them extremely easy to use and provides “bust proof” operation similar to that obtained with 3-pin linear regulators.

The LT1271/LT1269 operate with supply voltages from 3.5V to 30V, and draw only 7mA quiescent current. By utilizing current mode switching techniques, they provides excellent AC and DC load and line regulation.

A patented adaptive antisat switch drive allows very wide ranging load currents with no loss in efficiency. An externally activated shutdown mode reduces total supply current to 100µA typical for standby operation.

User Note: This data sheet is only intended to provide specifications, graphs, and a general functional description of the LT1271/LT1269. Application circuits are included to show the capability of the LT1271/LT1269. A complete design manual (AN-19) should be obtained to assist in developing new designs. This manual contains a comprehensive discussion of both the LT1070 and the external components used with it, as well as complete formulas for calculating the values of these components. The manual can also be used for the LT1271/LT1269 by factoring in the higher switch current rating and higher operating frequency.

Applications

* Boost Converter

* High Efficiency Buck Converter

* PC Power Supply with Multiple Outputs

* Battery Up-Converter

* Negative-to-Positive Converter

* Wide Input Voltage Range 3.5V to 30V

* Low Quiescent Current: 7mA

* Internal 4A Switch

* Very Few External Parts Required

* Self Protected Against Overloads

* Shutdown Mode Draws Only 100µA Supply Current

* Flyback Regulated Mode Has Fully Floating Outputs

* Comes in Standard 5-Pin Package

* Can Be Externally Synchronized (See LT1072 Data Sheet)