ADP1108

a FEATURES Operates at Supply Voltages From 2.0 V to 30 V Consumes Only 110 ␮A Supply Current Step-Up or Step-Down Mode Operation Minimum External Components Required Low Battery Detector Comparator On-Chip User-Adjustable Current Limit Internal 1 A Power Switch Fixed or Adjustable Output Voltage Versions 8-Pin DIP or SO-8 Package APPLICATIONS Notebook/Palm Top Computers 3 V to 5 V, 5 V to 12 V Converters 9 V to 5 V, 12 V to 5 V Converters LCD Bias Generators Peripherals and Add-On Cards Battery Backup Supplies Cellular Telephones Portable Instruments Micropower DC-DC Converter Adjustable and Fixed 3.3 V, 5 V, 12 V ADP1108 FUNCTIONAL BLOCK DIAGRAMS SET ADP1108 A2 VIN GAIN BLOCK/ ERROR AMP 1.245V REFERENCE ILIM SW1 A1 OSCILLATOR DRIVER SW2 AO COMPARATOR GND FB SET ADP1108-3.3 ADP1108-5 ADP1108-12 VIN A2 GAIN BLOCK/ ERROR AMP 1.245V REFERENCE A1 OSCILLATOR DRIVER SW2 AO ILIM SW1 GENERAL DESCRIPTION The ADP1108 is a highly versatile micropower switch-mode dc-dc converter that operates from an input voltage supply as low as 2.0 V and typically starts up from 1.8 V. The ADP1108 can be programmed into a step-up or step-down dc-to-dc converter with only three external components. The fixed outputs are 3.3 V, 5 V and 12 V. An adjustable version is also available. In step-up mode, supply voltage range is 2.0 V to 12 V, and 30 V in step-down mode. The ADP1108 can deliver 150 mA at 5 V from a 2 AA cell input and 300 mA at 5 V from a 9 V input in step-down mode. Switch current lim...