Datasheet LT3845A (Analog Devices)

LT3845A High Voltage Synchronous Current Mode Step-Down Controller with Adjustable Operating Frequency
FEATURES DESCRIPTION
n
High Voltage Operation: Up to 60V
The LT®3845A is a high voltage, synchronous, current n
Synchronizable Up to 600kHz
mode controller used for medium to high power, high n
Adjustable Constant Frequency: 100kHz to 500kHz
efficiency supplies. It offers a wide 4V to 60V input range n
Output Voltages Up to 36V
(7.5V minimum start-up voltage). An onboard regulator n
Stable Operation in Current Limit
simplifies the biasing requirements by providing IC power n Adaptive Nonoverlap Circuitry Prevents Switch directly from VIN. Shoot-Through Burst Mode® operation maintains high efficiency at light n Reverse Inductor Current Inhibit for Discontinuous loads by reducing IC quiescent current to 120µA. Light load Operation Improves Efficiency with Light Loads efficiency is also improved with the reverse inductor current n Programmable Soft-Start inhibit function which supports discontinuous operation. n 120µA No Load Quiescent Current n 10µA Shutdown Supply Current Additional features include adjustable fixed operating n 1% Regulation Accuracy frequency that can be synchronized to an external clock n Standard Gate N-Channel Power MOSFETs for noise sensitive applications, gate drivers capable of n Reverse Overcurrent Protection driving large N-channel MOSFETs, a precision undervoltage n 16-Lead Thermally Enhanced TSSOP Package lockout, 10µA shutdown current, short-circuit protection
APPLICATIONS
and a programmable soft-start. The LT3845A is available in a 16-lead thermally enhanced n 12V and 42V Automotive and Heavy Equipment TSSOP package. n 48V Telecom Power Supplies L, LT, LTC, LTM, Burst Mode, Linear Technology and the Linear logo are registered trademarks of n Avionics and Industrial Control Systems Linear Technology Corporation. All other trademarks are the property of their respective owners.. Protected by U.S. Patents, including 5481178, 6611131, 6304066, 6498466, 6580258. n Distributed Power Converters
TYPICAL APPLICATION High Voltage Step-Down Regulator 48V to 12V at 75W Efficiency and Power Loss
V
vs Load Current
IN 20V TO 55V 0.1µF 2.2µF 100 7 100V 1M V VIN = 48V IN BOOST 47µF 95 6 63V SHDN TG Si7370DP 1500pF LT3845A BAS521 15µH 0.008Ω VOUT 90 5 POWER LOSS (W) 82.5k CSS SW 12V 75W 85 4 BURST_EN VCC B160 33µF Si7370DP VFB BG ×3 80 3 20k EFFICIENCY(%) 16.2k VC PGND 75 2 100pF SYNC SENSE+ LOSS 70 1 fSET SENSE– 1µF 2200pF 143k 49.9k SGND 1N4148 65 0 0.1 1 10 LOAD CURENT (A) 3845A TA01a 3845A TA01b 3845afa 1 Document Outline Features Applications Description Typical Application Absolute Maximum Ratings Pin Configuration Order Information Electrical Characteristics Typical Performance Characteristics Pin Functions Block Diagram Applications Information Typical Applications Package Description Revision History Typical Application Related Parts