LTC3873 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 is a constant frequency current mode, n Internal or Programmable External Soft-Start boost, flyback or SEPIC DC/DC controller that drives an n Constant Frequency 200kHz Operation N-channel power MOSFET in high input and output volt- n Adjustable Current Limit age converter applications. Soft-start can be programmed n Current Sense Resistor Optional using an external capacitor. n Maximum 60V on SW Node with RDS(ON) Sensing The LTC3873 provides ±1.5% output voltage accuracy and n ±1.5% Voltage Reference Accuracy consumes only 300μA quiescent current during normal n Current Mode Operation for Excellent Line and Load operation and only 55μA during micropower start-up. Transient Response Using a 9.3V internal shunt regulator, the LTC3873 can n Low Quiescent Current: 300µA be powered from a high input voltage through a resistor n Low Profile (1mm) ThinSOTTM and (0.75mm) or it can be powered directly from a low impedance DC 2mm × 3mm DFN Package voltage of 9V or less. APPLICATIONS The LTC3873 is available in 8-lead ThinSOT and 2mm × 3mm DFN packages. n Telecom Power Supplies PARAMETERLTC3873LTC3873-5 n 42V and 12V Automotive Power Supplies VCC UV+ 8.4V 4.1V V n Portable Electronic Equipment CC UV– 4V 2.9V 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 APPLICATION5V Output Nonisolated Telecom Power SupplyEfficiency and Power Loss vs Load Current VIN 36V TO 72V D2 100 3000 VOUT T1 5V 90 4.7µF • 100µF 2A MAX EFFICIENCY 2500 100V 221k D1 6.3V 80 X5R X5R POWER LOSS (mW) 70 • ×3 2000 10µF 60 10V X5R 50 V 1500 CC POWER LOSS ITH NGATE M1 40 EFFICIENCY (%) 7.5k LTC3873 1000 30 RUN/SS VIN = 72V 2.2nF 0.1µF 20 GND SW VIN = 60V 500 VIN = 48V IPRG 10 68mΩ VIN = 36V VFB 0 10 10 1000 12.1k 38.3k LOAD CURRENT (mA) 3873 TA01a 3873 TA01b 3873fb For more information www.linear.com/LTC3873 1
