LTC3873-5 No RSENSETM Constant Frequency Current Mode Boost/Flyback/SEPIC DC/DC Controller FEATURESDESCRIPTION n VIN and VOUT Limited Only by External Components The LTC®3873-5 is a constant frequency current mode n Internal or Programmable External Soft-Start controller for boost, fl yback or SEPIC DC/DC converters n Constant Frequency 200kHz Operation designed to drive an N-channel MOSFET for high input n Adjustable Current Limit and output voltage converter applications. n Current Sense Resistor Optional The LTC3873-5 provides ±1.5% output voltage accuracy n ±1.5% Voltage Reference Accuracy and consumes only 300μA quiescent current during nor- n Current Mode Operation for Excellent Line and Load mal operation and only 50μA during micropower start-up. Transient Response Using a 9.3V internal shunt regulator, the LTC3873-5 can n 4.1V Undervoltage Threshold for Logic Level be powered from a high input voltage through a resistor MOSFET Applications or it can be powered directly from a low impedance DC n Low Quiescent Current: 300μA voltage of 9V or less. Soft-start can be programmed using n Low Profi le (1mm) ThinSOTTM and (0.75mm) an external capacitor. 2mm × 3mm DFN Package The LTC3873-5 is available in 8-lead ThinSOT and 2mm APPLICATIONS × 3mm DFN packages. n PARAMETERLTC3873LTC3873-5 Telecom Power Supplies V n Automotive Power Supplies CC UV+ 8.4V 4.1V VCC UV– 4V 2.9V n PoE Applications L, LT, LTC and LTM are registered trademarks of Linear Technology Corporation. No RSENSE and ThinSOT are trademarks of Linear Technology Corporation. All other trademarks are the property of their respective owners. TYPICAL APPLICATIONHigh Effi ciency 5V Input, 12V Output Boost ConverterEffi ciency and Power Loss vs Load Current 100 10000 1nF 90 4.7nF RUN/SS 11.8k 80 V I IN POWER LOSS (mW) TH VCC 5V 70 47pF 1000 LTC3873-5 10μF 10μH 60 IPRG V 50 OUT GND SW 12V 12k 40 2A EFFICIENCY (%) V 100 FB NGATE 22μF 30 108k 20 38735 TA01a 10 0 10 10 100 1000 IOUT (mA) 3873 TA01b 38735fb 1
