LTC3803 Constant Frequency Current Mode Flyback DC/DC Controller in ThinSOT FEATURESDESCRIPTION n VIN and VOUT Limited Only by External Components The LTC®3803 is a constant frequency current mode fl yback n Adjustable Slope Compensation controller optimized for driving N-channel MOSFETs in high n Internal Soft-Start input voltage applications. Constant frequency operation n Constant Frequency 200kHz Operation is maintained down to very light loads, resulting in less n ±1.5% Reference Accuracy low frequency noise generation over a wide range of load n Current Mode Operation for Excellent Line and Load currents. Slope compensation can be programmed with Transient Response an external resistor. n No Minimum Load Requirement The LTC3803 provides ±1.5% output voltage accuracy and n Low Quiescent Current: 240μA consumes only 240μA of quiescent current. Ground-refer- n Low Profi le (1mm) SOT-23 Package enced current sensing allows LTC3803-based converters to accept input supplies beyond the LTC3803’s absolute APPLICATIONS maximum VCC. A micropower hysteretic start-up feature allows effi cient operation at high input voltages. For sim- n Telecom Power Supplies plicity, the LTC3803 can also be powered from a high VIN n 42V and 12V Automotive Power Supplies through a resistor, due to its internal shunt regulator. An n Auxiliary/Housekeeping Power Supplies internal undervoltage lockout shuts down the LTC3803 n Power Over Ethernet when the input voltage is too low to provide suffi cient L, LT, LTC, LTM, Burst Mode, Linear Technology and the Linear logo are registered trademarks gate drive to the external MOSFET. and ThinSOT and No RSENSE are trademarks of Linear Technology Corporation. All other trademarks are the property of their respective owners. The LTC3803 is available in a low profi le (1mm) 6-lead SOT-23 (ThinSOT™) package. TYPICAL APPLICATION5V Output Nonisolated Telecom Housekeeping Power SupplyEffi ciency vs Load Current V 90 IN 36V TO 72V UPS840 V 80 VIN = 36V OUT T1 5V • 4.7μF 300μF* 2A MAX 70 10k V 100V 6.3V IN = 48V 60 X5R X5R 10μF • VIN = 60V 50 10V X5R V V IN = 72V CC 40 ITH/RUN NGATE FDC2512 EFFICIENCY (%) 30 56k LTC3803 20 GND SENSE 0.0022μF VFB 68mΩ 10 0 20k 105k 0.1 1 10 3803 TA01 IOUT (A) T1: COOPER CTX02-15242 *THREE 100μF UNITS IN PARALLEL 3803 TA02 3803fc 1 Document Outline FEATURES DESCRIPTION APPLICATIONS 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 APPLICATIONS RELATED PARTS
