Step-Down Switching Regulator

The LT1176 is a 1A monolithic bipolar switching regulator which requires only a few external parts for normal operation. The power switch, all oscillator and control circuitry and all current limit components are included on the chip. The topology is a classic positive buck configuration but several design innovations allows this device to be used as a positive-to-negative converter, a negative boost converter, and as a flyback converter. The switch output is specified to swing below ground.

The LT1176 uses a true analog multiplier in the feedback loop. This makes the device respond nearly instantaneously to input voltage fluctuations and makes loop gain independent of input voltage. As a result, dynamic behavior of the regulator is significantly improved over previous designs.

On-chip pulse by pulse current limiting makes the LT1176 nearly bust proof for output overloads or shorts. The input voltage range as a buck converter is 8V to 35V, but a self boot feature allows input voltages as low as 5V in the inverting and boost configurations.

The LT1176 is available in a low cost 8-lead DIP package with frequency preset at 100kHz and current limit at 1.7A. An adjustable output is offered as well as a preset 5V version. For further design details and application help, see the LT1074/LT1076 data sheet and Application Note 44.

Applications

* Buck Converter with Output Voltage Range of 2.5V to 30V

* Positive-to-Negative Converter

* Negative Boost Converter

* Multiple Output Buck Converter

* 1.2A Onboard Switch

* 100kHz Switching Frequency

* Excellent Dynamic Behavior

* DIP and Surface Mount Packages

* Only 8mA Quiescent Current

* Preset 5V Output Available

* Operates Up to 35V Input

* Micropower Shutdown Mode