LT1108 Micropower DC/DC Converter Adjustable and Fixed 5V, 12V EATURES DESCRIPTIO F n Operates at Supply Voltages from 2V to 30V The LT1108 is a versatile micropower DC/DC converter. n Consumes Only 110A Supply Current The device requires only four external components to n Works in Step-Up or Step-Down Mode deliver a fixed output of 5V or 12V. Supply voltage ranges n Only Four External Components Required from 2V to 12V in step-up mode and to 30V in step-down n Low Battery Detector Comparator On-Chip mode. The LT1108 functions equally well in step-up, step- n User Adjustable Current Limit down, or inverting applications. n Internal 1A Power Switch The LT1108 is pin-for-pin compatible with the LT1173, but n Fixed or Adjustable Output Voltage Versions has a duty cycle of 70%, resulting in increased output n Space Saving 8-Pin MiniDIP or S8 Package current in many applications. The LT1108 can deliver 150mA at 5V from a 2 AA cell input and 5V at 300mA from 9V in step-down mode. Quiescent current is just 110A, APPLICATI S making the LT1108 ideal for power conscious battery- n Palmtop Computers operated systems. n 3V to 5V, 5V to 12V Converters n 9V to 5V, 12V to 5V Converters Switch current limit can be programmed with a single n LCD Bias Generators resistor. An auxiliary gain block can be configured as a low n Peripherals and Add-On Cards battery detector, linear post regulator, undervoltage lock- n Battery Backup Supplies out circuit, or error amplifier. n Cellular Telephones n Portable Instruments TYPICAL APPLICATI Palmtop Computer Logic Supply Efficiency 84 L1* 1N5817 100H 5V 82 150mA V = 3V IN 47 80 V = 2.5V IN I V LIM IN 78 V = 2V IN SW1 AVX + + 2 AA TPS 76 100F LT1108-5 CELLS 330F 6.3V SENSE 74 GND SW2 72 70 1 10 100 *L1 = GOWANDA GA20-103K LT1108 TA01 COILTRONICS CTX100-4 LOAD CURRENT (mA) SUMIDA CD105-101K LT1108 TA02 1 EFFICIENCY (%) UO UO ULT1108 ABSOLUTEXAI U RATI GS Supply Voltage (V ) ............................................... 36V Maximum Power Dissipation ............................ 500mW IN SW1 Pin Voltage (V ) ......................................... 50V Maximum Switch Current ...................................... 1.5A SW1 SW2 Pin Voltage (V ) ............................ 0.5V to V Operating Temperature Range .................... 0C to 70C SW2 IN Feedback Pin Voltage (LT1108) ............................. 5.5V Storage Temperature Range ................ 65C to 150C Sense Pin Voltage (LT1108, -5, -12) ...................... 36V Lead Temperature (Soldering, 10 sec)................. 300C / PACKAGE ORDER I FOR ATIO ORDER PART ORDER PART TOP VIEW TOP VIEW NUMBER NUMBER I 1 FB (SENSE*) I 1 8 FB (SENSE*) 8 LIM LIM LT1108CN8 LT1108CS8 V SET V 2 7 SET 2 7 IN IN LT1108CN8-5 LT1108CS8-5 SW1 3 6 A0 SW1 3 6 A0 LT1108CN8-12 LT1108CS8-12 SW2 4 GND SW2 4 5 GND 5 S8 PART MARKING N8 PACKAGE S8 PACKAGE 8-LEAD PLASTIC DIP 8-LEAD PLASTIC SOIC *FIXED VERSIONS *FIXED VERSIONS 1108 10805 T = 90C, = 130C/W JMAX JA T = 90C, = 150C/W JMAX JA 10812 ELECTRICAL CHARACTERISTICS T = 25C, V = 3V, unless otherwise noted. A IN SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS I Quiescent Current Switch OFF l 110 150 A Q Quiescent Current, Boost Mode Configuration No Load LT1108-5 135 A LT1108-12 250 A V Input Voltage Step-Up Mode l 2 12.6 V IN Step-Down Mode l 30.0 V Comparator Trip Point Voltage LT1108 (Note 1) l 1.2 1.245 1.3 V V Output Sense Voltage LT1108-5 (Note 2) l 4.75 5 5.25 V OUT LT1108-12 (Note 2) l 11.4 12 12.6 V Comparator Hysteresis LT1108 l 510 mV Output Hysteresis LT1108-5 l 20 40 mV LT1108-12 l 50 100 mV f Oscillator Frequency l 14 19 25 kHz OSC Duty Cycle Full Load, Step-Up Mode l 63 70 78 % t Switch-ON Time I Tied to V , Step-Up Mode l 28 36 48 s ON LIM IN Feedback Pin Bias Current LT1108, V = 0V l 10 50 nA FB Set Pin Bias Current V = V l 20 100 nA SET REF V Gain Block Output Low I = 100A, V = 1V l 0.15 0.4 V OL SINK SET Reference Line Regulation 2V V 5V l 0.20 0.400 %/V IN 5V V 30V l 0.02 0.075 %/V IN V SW Voltage, Step-Up Mode V = 3V, I = 650mA l 0.5 0.65 V SAT SAT IN SW V = 5V, I = 1A 0.8 1.00 V IN SW 2 U WU U W W W