LTC3805-5 Adjustable Frequency Current Mode Flyback/ Boost/SEPIC DC/DC Controller FEATURESDESCRIPTION n VIN and VOUT Limited Only by External Components The LTC®3805-5 is a current mode DC/DC controller de- n 4.5V Undervoltage Lockout Threshold signed to drive an N-channel MOSFET in flyback, boost n Adjustable Slope Compensation and SEPIC converter applications. Operating frequency n Adjustable Overcurrent Protection with Automatic and slope compensation can be programmed by external Restart resistors. Programmable overcurrent sensing protects n Adjustable Operating Frequency (70kHz to 700kHz) the converter from overload and short-circuit conditions. With One External Resistor Soft-start can be programmed using an external capacitor n Synchronizable to an External Clock and the soft-start capacitor also programs an automatic n ±1.5% Reference Accuracy restart feature. n Only 100mV Current Sense Voltage Drop The LTC3805-5 provides ±1.5% output voltage accuracy n RUN Pin with Precision Threshold and Adjustable and consumes only 360µA of quiescent current during Hysteresis normal operation and only 40µA during micropower start- n Programmable Soft-Start with One External Capacitor up. Using a 9.5V internal shunt regulator, the LTC3805-5 n Low Quiescent Current: 360µA can be powered from a high VIN through a resistor or it n Small 10-Lead MSOP and 3mm × 3mm DFN can be powered directly from a low impedance DC voltage from 4.7V to 8.8V. APPLICATIONS The LTC3805-5 is available in the 10-lead MSOP package n Automotive Power Supplies and the 3mm × 3mm DFN package. n Telecom Power Supplies L, LT, LTC, LTM, Burst Mode, Linear Technology and the Linear logo are registered n Isolated Electronic Equipment trademarks, No RSENSE and ThinSOT are trademarks of Linear Technology Corporation. All other trademarks are the property of their respective owners. n Auxiliary/Housekeeping Power Supplies n Power over Ethernet TYPICAL APPLICATION5V to 12V/1A Boost ConverterEfficiency and Power Loss vs Load Current 100 2.5 4.3µH UPS840 V V OUT IN 12V 5V 95 2.0 22µF 1A 5V EFFICIENCY ×2 100µF V POWER LOSS (W) CC 8.5V EFFICIENCY RUN GATE 90 1.5 LTC3805-5 1.33k 8.5V LOSS ITH OC 5V LOSS 3k SSFLT I 191k 85 1 SENSE EFFICIENCY (%) 20k 0.1µF FS FB SYNC GND 80 0.5 470pF 118k 8mΩ 13.7k 38055 TA01a 75 0 0.01 0.1 1 10 LOAD CURRENT (A) 38055TA01b 38055fe 1 Document Outline Features Applications Description Typical Application Absolute Maximum Ratings Pin Configuration order information Electrical Characteristics Typical Performance Characteristics Pin Functions Block Diagram Operation Applications Information Typical Applications Package Description Revision History Typical Application Related Parts
