LT1108 Datasheet | Linear Technology

LT1108 Micropower DC/DC Converter Adjustable and Fixed 5V, 12V Features s s s s s s s s s DESCRIPTIO Operates at Supply Voltages from 2V to 30V Consumes Only 110µA Supply Current Works in Step-Up or Step-Down Mode Only Four External ponents Required Low Battery Detector parator On-Chip User Adjustable Current Limit Internal 1A Power Switch Fixed or Adjustable Output Voltage Versions Space Saving 8-Pin Mini DIP or S8 Package The LT1108 is a versatile micropower DC/DC converter. The device requires only four external ponents to deliver a fixed output of 5V or 12V. Supply voltage ranges from 2V to 12V in step-up mode and to 30V in step-down mode. The LT1108 functions equally well in step-up, stepdown, or inverting applications. The LT1108 is pin-for-pin patible with the LT1173, but has a duty cycle of 70%, resulting in increased output current in many applications. The LT1108 can deliver 150m A at 5V from a 2 AA cell input and 5V at 300m A from 9V in step-down mode. Quiescent current is just 110µA, making the LT1108 ideal for power conscious batteryoperated systems. Switch current limit can be programmed with a single resistor. An auxiliary gain block can be configured as a low battery detector, linear post regulator, undervoltage lockout circuit, or error amplifier. APPLICATI s s s s s s s s Palmtop puters 3V to 5V, 5V to 12V Converters 9V to 5V, 12V to 5V Converters LCD Bias Generators Peripherals and Add-On Cards Battery Backup Supplies Cellular Telephones Portable Instruments TYPICAL APPLICATI Palmtop puter Logic Supply L1- 100µH 47Ω ILIM 2 × AA CELLS VIN SW1 EFFICIENCY (%) 84 1N5817 5V 150m A 82 80 78 76 74 72 70 VIN = 3V VIN = 2.5V VIN = 2V + 100µF + LT1108-5 SENSE GND SW2 AVX TPS 330µF 6.3V - L1 = GOWANDA GA20-103K COILTRONICS CTX100-4 SUMIDA CD105-101K - TA01 Efficiency 1 10 100 LOAD CURRENT (m A) - TA02 LT1108 ABSOLUTE AXI U RATI GS Maximum Power Dissipation ............................ 500m W...