Datasheet LT1725 (Analog Devices)

HerstellerAnalog Devices
BeschreibungGeneral Purpose Isolated Flyback Controller
Seiten / Seite28 / 1 — FEATURES. DESCRIPTIO. Drives External Power MOSFET with External. SENSE …
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DokumentenspracheEnglisch

FEATURES. DESCRIPTIO. Drives External Power MOSFET with External. SENSE Resistor. Application Input Voltage Limited Only by

Datasheet LT1725 Analog Devices

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LT1725 General Purpose Isolated Flyback Controller
U FEATURES DESCRIPTIO

Drives External Power MOSFET with External
The LT®1725 is a monolithic switching regulator control-
I
ler specifically designed for the isolated flyback topology.
SENSE Resistor

Application Input Voltage Limited Only by
It drives the gate of an external MOSFET and is generally
External Power Components
powered from a third transformer winding. These features ■
Senses Output Voltage Directly from Primary Side
allow for an application input voltage limited only by
Winding—No Optoisolator Required
external power path components. The third transformer ■ Accurate Regulation Without User Trims winding also provides output voltage feedback informa- ■ Regulation Maintained Well into Discontinuous Mode tion, such that an optoisolator is not required. Its gate ■ Switching Frequency from 50kHz to 250kHz with drive capability coupled with a suitable external MOSFET External Capacitor can deliver load power up to tens of watts. ■ Optional Load Compensation The LT1725 has a number of features not found on most ■ Optional Undervoltage Lockout other switching regulator ICs. By utilizing current mode ■ Available in 16-Pin SO and SSOP Packages switching techniques, it provides excellent AC and DC line regulation. Its unique control circuitry can maintain regu-
U
lation well into discontinuous mode in most applications.
APPLICATIO S
Optional load compensation circuitry allows for improved ■ Telecom Isolated Converters load regulation. An optional undervoltage lockout pin ■ Offline Isolated Power Supplies halts operation when the application input voltage is too ■ Instrumentation Power Supplies low. An optional external capacitor implements a soft- start function. A 3V output is available at up to several mA , LTC and LT are registered trademarks of Linear Technology Corporation. All other trademarks are the property of their respective owners. for powering primary side application circuitry.
U TYPICAL APPLICATIO 48V to Isolated 5V Converter
CTX02-14989
Output Load Regulation
6 470pF LT1725 5.25 18Ω 35.7k VIN 36V TO 72V 3VOUT BAS16 1% 1 VIN = 48V FB 22Ω VIN = 36V 47k 3.01k V SFST V OUT = 5V CC 1% V 1nF + 2 9 IOUT = 0 to 2A IN = 72V 15µF 1µF 12CWQ06 (V) VC 51Ω 5.00 47pF 68Ω OUT 1W V OSCAP 11 820k 150pF tON UVLO 51k 10 + 100pF 33k 1.5µF 150µF ENDLY 51k 4 12 4.75 MENAB 0 0.5 1.0 1.5 2.0 51k ILOAD (A) ROCMP GATE IRF620 2.7k 1725 F10b RCMPC ISENSE 0.1µF SGND PGND 0.18Ω 1725 TA01a 1725fa 1