Datasheet LTC3805 (Analog Devices)

LTC3805 Adjustable Frequency Current Mode Flyback DC/DC Controller
Features Description
n
VIN and VOUT Limited Only by External Components
The LTC®3805 is a current mode controller for flyback n
Adjustable Slope Compensation
DC/DC converters designed to drive an N-channel MOSFET n
Adjustable Overcurrent Protection with Automatic
in high input and output voltage converter applications.
Restart
Operating frequency and slope compensation can be n
Adjustable Operating Frequency (70kHz to 700kHz)
programmed by external resistors. Programmable overcur-
with One External Resistor
rent sensing protects the converter from short-circuits. n Synchronizable to an External Clock Soft-start can be programmed using an external capacitor n ±1.5% Reference Accuracy and the soft-start capacitor also programs an automatic n Current Mode Operation for Excellent Line and Load restart feature. Transient Response The LTC3805 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 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 of 9V or less.
applications
The LTC3805 is available in the 10-lead MSOP package n Telecom Power Supplies and the 3mm × 3mm DFN package. n 42V and 12V Automotive Power Supplies L,LT, LTC, LTM, Burst Mode, Linear Technology and the Linear logo are registered trademarks, No R n Isolated Electronic Equipment SENSE and ThinSOT are trademarks of Linear Technology Corporation. All other trademarks are the property of their respective owners.
typical application 36V – 72V to 5V/2A Nonisolated Flyback Converter Efficiency and Power Loss vs Load Current; V
V
O = 5V
V OUT IN 5V 100 10 36V TO AT 2A VIN = 48V 72V 2.2µF 90 ×2 221k 100k 100µF × 2 80 POWER LOSS (W) 70 EFFICIENCY 22µF 60 8.66k 50 1 V LOSS CC 40 RUN GATE EFFICIENCY (%) 30 LTC3805 1.33k ITH OC 20 3k SSFLT I 71.5k SENSE 10 20k 0.1µF FS FB 0 0.1 0.01 0.1 1 10 SYNC GND 470pF 118k 68mΩ 13.7k LOAD CURRENT (A) 3805 TA01b 3805 TA01a 3805fg 1 Document Outline Features Applications Description Typical Application Absolute Maximum Ratings Pin Configuration 0rder Information Electrical Characteristics Typical Performance Characteristics Pin Functions Block Diagram Operation Applications Information Typical Application Package Description Revision History Typical Application Related Parts