Datasheet LT3781 (Analog Devices)

FabricanteAnalog Devices
DescripciónBootstrap Start Dual Transistor Synchronous Forward Controller
Páginas / Página20 / 1 — FEATURES. DESCRIPTIO. High Voltage Operation up to 72V. Synchronizable …
Formato / tamaño de archivoPDF / 260 Kb
Idioma del documentoInglés

FEATURES. DESCRIPTIO. High Voltage Operation up to 72V. Synchronizable Operating Frequency and Output

Datasheet LT3781 Analog Devices

Línea de modelo para esta hoja de datos

Versión de texto del documento

LT3781 “Bootstrap” Start Dual Transistor Synchronous Forward Controller
U FEATURES DESCRIPTIO

High Voltage Operation up to 72V
The LT®3781 controller simplifies the design of high ■
Synchronizable Operating Frequency and Output
power synchronous dual transistor forward DC/DC con-
Switch Phase for Multiple Controller Systems
verters. The part employs fixed frequency current mode ■
Synchronous Switch Output
control and supports both isolated and nonisolated to- ■
Undervoltage Lockout Protection with 6V Hysteresis
pologies. The IC drives external N-channel power MOSFETs
for Self-Biased Power
and operates with input voltages up to 72V. ■ Fixed Frequency Operation to 350kHz The LT3781 is ideal for output derived power schemes, ■ Local ±1% Voltage Reference through the use of a large undervoltage lockout hysteresis ■ Input Overvoltage Protection range. The part is also equipped with an 18V VCC shunt ■ Low Start-Up Current regulator, which prevents exceeding absolute maximum ■ Programmable Start Inhibit for Power Supply ratings while in trickle start applications. Sequencing and Protection ■ Optocoupler Support The LT3781’s operating frequency is programmable and ■ can be synchronized up to 350kHz. Switch phase is also
U
Soft-Start Control controlled during synchronized operation to accommo-
APPLICATIO S
date multiple-converter systems. Internal logic guaran- ■ Isolated Telecommunication Systems tees 50% maximum duty cycle operation to prevent trans- ■ Personal Computers and Peripherals former saturation. ■ Distributed Power Step-Down Converters The LT3781 is available in a 20-lead SSOP package. ■ Lead Acid Battery Backup Systems , LTC and LT are registered trademarks of Linear Technology Corporation. ■ Automotive and Heavy Equipment
U TYPICAL APPLICATIO 36V-72V to 5V/7A DC/DC Synchronous Forward Converter (Quarter-Brick Footprint)
L1 L2 VOUT = 5V T1 4.7µH 4.7µH I • OUT = 7A V + + 6 IN VOUT Q1 1 7 2 10Ω MURS120T3 3 0.25W + + C2 C5 C4 • • MBR- 5 22µF 330µF 1.5µF 1nF 0540T1 MURS120T3 100V 10V 100V 8 100V 10 1nF Q6 10 11 Ω R9 • 100V 4 C3 Q3 0.25W 12 0.025Ω 1.5µF 1/2W 9 100V 4.7Ω Q5 V – – IN VOUT ZVN3310F BAT54 1OV 10k BIAS 1OV 100Ω 2k 0.1µF BIAS FZT690 0.22µF MMBD914LT1 330pF 50V 100V 270k 73.2k CMPZ5242B 4.7µF 0.25W 1% 12V 5V 16V BAS21 20k OUT 20 19 18 15 11 14 13 V LTC1693-2 CC V TG BSTREF BG SENSE PGND 3.3k BST 12 8 6 2 SG VCC1 VCC2 OVLO LT3781 0.047µF 3 5 1 9 IN2 OUT2 SHDN 5VREF FSET THERM SYNC SGND SS VC VFB 1 7 IN1 OUT1 1nF 5 6 3 7 4 8 10 3.01k 51Ω 0.1µF 1.24k 4 2 52.3k 1% 1% 100Ω GND2 GND1 C2:SANYO 100MV22AX L2: PANASONIC ETQP6F4R1LF4 6.8k + 68µF C3, C4: VITRAMON VJ1825Y155MXB Q1,Q3:100V SILICONIX SUD40N10-25 10k 1µF 150pF 20V 4.7nF 1k C5: 4X KEMET T510X337KO10AS Q5,Q6: SILICONIX Si4450 0.01µF 1% L1: COILCRAFT DO1608C-472 T1:COILTRONICS VP5-1200 3781f 1