Features: 1.2A On-Board 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 ModeApplicationBuck Converter with Output Voltage Range of
2.5V to 30V
Positive-to-Negative Converter
Negative Boost Converter
Mulitple Output Buck ConverterSpecificationsInput Voltage.......................................................... 38V
Switch Voltage With Respect to Input Voltage........ 50V
Switch Voltage With Respect to Ground Pin
(VSW Negative) (Note 6)......................................... 20V
Feedback Pin Voltage.......................................2V, 10V
Shutdown Pin Voltage (Not to Exceed VIN)............. 35V
Status Pin Voltage
(Current Must Be Limited to 5mA When Status Pin
Switches "ON")................................................... 30V
ILIM Pin Voltage (Forced)........................................ 5.5V
Maximum Operating Ambient Temperature Range
LT1176C/LT1176C-5................................... 0°C to 70°C
Maximum Operating Junction Temperature Range
LT1176C/LT1176C-5................................. 0°C to 125°C
Storage Temperature Range................. 65°C to 150°C
Lead Temperature (Soldering, 10 sec) .................300°CDescriptionThe LT1176 is a 1A monolithic bipolar switching regulator which requires only a few external parts for normal opera-tion. 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 con- verter, 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 indepen- dent 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.
LT1176 Data Sheet
