Datasheet LT1950 (Analog Devices)
| Manufacturer | Analog Devices |
| Description | Single Switch PWM Controller with Auxiliary Boost Converter |
| Pages / Page | 20 / 1 — FEATURES. DESCRIPTIO. Wide Input Range: 3V to 25V. Programmable … |
| File Format / Size | PDF / 223 Kb |
| Document Language | English |
FEATURES. DESCRIPTIO. Wide Input Range: 3V to 25V. Programmable Volt-Second Clamp. Output Power Levels from 25W to 500W
Model Line for this Datasheet
Text Version of Document
LT1950 Single Switch PWM Controller with Auxiliary Boost Converter
U FEATURES DESCRIPTIO
■
Wide Input Range: 3V to 25V
The LT®1950 is a wide input range, forward, boost, flyback ■
Programmable Volt-Second Clamp
and SEPIC controller that drives an N-channel power ■
Output Power Levels from 25W to 500W
MOSFET with few external components required. ■
Auxiliary Boost Converter Provides 10V Gate Drive
A resistor programmable duty cycle clamp can be used to
from VIN as Low as 3V
generate a volt-second clamp for forward converter appli- ■
Programmable Operating Frequency (100kHz to
cations. An internal boost switcher is available for creating
500kHz) with One External Resistor
a separate supply for the output gate driver, allowing 10V ■
Programmable Slope Compensation
gate drive from input voltages as low as 3V. The LT1950’s ■
Programmable Leading Edge Blanking
operating frequency can be set with an external resistor ■ ±2% Internal 1.23V Reference over a 100kHz to 500kHz range and a SYNC pin allows the ■ Accurate Shutdown Pin Threshold with part to be synchronized to an external clock. Additional Programmable
Hysteresis programmability exists for leading edge blanking and ■ 60ns Current Sense Delay slope compensation. ■ 2.5V Auxiliary Reference Output ■ Synchronizable to an External Clock up to 1.5 • f A fast current sense comparator achieves 60ns current OSC ■ Current Mode Control sense delay and the error amplifier is a true voltage mode ■ Small 16-Pin SSOP Package error amplifier, allowing a wide range of compensation
U
networks. An accurate shutdown pin with programmable
APPLICATIO S
hysteresis is available for undervoltage lockout and shut- ■ Telecom Power Supplies down. The LT1950 is available in a small 16-Pin SSOP ■ Automotive Power Supplies package. ■ Portable Electronic Equipment ■ Isolated and Nonisolated DC/DC Converters , LTC and LT are registered trademarks of Linear Technology Corporation.
U TYPICAL APPLICATIO 36V to 72V DC to 26V/5A (Single Switch) Forward Converter Efficiency vs Load Current
10V 95 BIAS VIN MBRB20200 47µH VOUT VIN = 36V 26V SLOPE VIN 5A 90 V 2.5V IN = 48V 470k 47µF VREF VIN2 VIN = 72V 0.1µF BOOST VSEC PA0581 85 ROSC SHDN 1µF 249k 18k LT1950 80 EFFICIENCY (%) BLANK GATE Si7450 SYNC ISENSE 75 GND PGND 0.015Ω FB COMP 70 4.99k 4.7k 0.5 1.5 2.5 3.5 4.5 5.5 0.022µF 100k LOAD CURRENT (A) 1950 TA01a 1950 TA01b 1950fa 1
U FEATURES DESCRIPTIO
■
Wide Input Range: 3V to 25V
The LT®1950 is a wide input range, forward, boost, flyback ■
Programmable Volt-Second Clamp
and SEPIC controller that drives an N-channel power ■
Output Power Levels from 25W to 500W
MOSFET with few external components required. ■
Auxiliary Boost Converter Provides 10V Gate Drive
A resistor programmable duty cycle clamp can be used to
from VIN as Low as 3V
generate a volt-second clamp for forward converter appli- ■
Programmable Operating Frequency (100kHz to
cations. An internal boost switcher is available for creating
500kHz) with One External Resistor
a separate supply for the output gate driver, allowing 10V ■
Programmable Slope Compensation
gate drive from input voltages as low as 3V. The LT1950’s ■
Programmable Leading Edge Blanking
operating frequency can be set with an external resistor ■ ±2% Internal 1.23V Reference over a 100kHz to 500kHz range and a SYNC pin allows the ■ Accurate Shutdown Pin Threshold with part to be synchronized to an external clock. Additional Programmable
Hysteresis programmability exists for leading edge blanking and ■ 60ns Current Sense Delay slope compensation. ■ 2.5V Auxiliary Reference Output ■ Synchronizable to an External Clock up to 1.5 • f A fast current sense comparator achieves 60ns current OSC ■ Current Mode Control sense delay and the error amplifier is a true voltage mode ■ Small 16-Pin SSOP Package error amplifier, allowing a wide range of compensation
U
networks. An accurate shutdown pin with programmable
APPLICATIO S
hysteresis is available for undervoltage lockout and shut- ■ Telecom Power Supplies down. The LT1950 is available in a small 16-Pin SSOP ■ Automotive Power Supplies package. ■ Portable Electronic Equipment ■ Isolated and Nonisolated DC/DC Converters , LTC and LT are registered trademarks of Linear Technology Corporation.
U TYPICAL APPLICATIO 36V to 72V DC to 26V/5A (Single Switch) Forward Converter Efficiency vs Load Current
10V 95 BIAS VIN MBRB20200 47µH VOUT VIN = 36V 26V SLOPE VIN 5A 90 V 2.5V IN = 48V 470k 47µF VREF VIN2 VIN = 72V 0.1µF BOOST VSEC PA0581 85 ROSC SHDN 1µF 249k 18k LT1950 80 EFFICIENCY (%) BLANK GATE Si7450 SYNC ISENSE 75 GND PGND 0.015Ω FB COMP 70 4.99k 4.7k 0.5 1.5 2.5 3.5 4.5 5.5 0.022µF 100k LOAD CURRENT (A) 1950 TA01a 1950 TA01b 1950fa 1
