LT1725
PRODUCTIONGeneral Purpose Isolated Flyback Controller
- Part Models
- 9
- 1ku List Price
- Starting From $4.61
Overview
- Drives External Power MOSFET with External ISENSE Resistor
- Application Input Voltage Limited Only by External Power Components
- Senses Output Voltage Directly from Primary Side Winding—No Optoisolator Required
- Accurate Regulation Without User Trims
- Regulation Maintained Well into Discontinuous Mode
- Switching Frequency from 50kHz to 250kHz with External Capacitor
- Optional Load Compensation
- Optional Undervoltage Lockout
- Available in 16-Pin SO and SSOP Packages
The LT1725 is a monolithic switching regulator controller specifically designed for the isolated flyback topology. It drives the gate of an external MOSFET and is generally powered from a third transformer winding. These features allow for an application input voltage limited only by external power path components. The third transformer winding also provides output voltage feedback information, such that an optoisolator is not required. Its gate drive capability coupled with a suitable external MOSFET can deliver load power up to tens of watts.
The LT1725 has a number of features not found on most other switching regulator ICs. By utilizing current mode switching techniques, it provides excellent AC and DC line regulation. Its unique control circuitry can maintain regulation well into discontinuous mode in most applications. Optional load compensation circuitry allows for improved load regulation. An optional undervoltage lockout pin halts operation when the application input voltage is too low. An optional external capacitor implements a soft-start function. A 3V output is available at up to several mA for powering primary side application circuitry.
Applications
- Telecom Isolated Converters
- Offline Isolated Power Supplies
- Instrumentation Power Supplies
Documentation
Data Sheet 1
User Guide 7
Design Note 2
Technical Articles 1
ADI has always placed the highest emphasis on delivering products that meet the maximum levels of quality and reliability. We achieve this by incorporating quality and reliability checks in every scope of product and process design, and in the manufacturing process as well. "Zero defects" for shipped products is always our goal. View our quality and reliability program and certifications for more information.
| Part Model | Pin/Package Drawing | Documentation | CAD Symbols, Footprints, and 3D Models |
|---|---|---|---|
| LT1725CGN#PBF | 16-Lead SSOP (Narrow 0.15 Inch) | ||
| LT1725CGN#TRPBF | 16-Lead SSOP (Narrow 0.15 Inch) | ||
| LT1725CS#PBF | 16-Lead SOIC (Narrow 0.15 Inch) | ||
| LT1725CS#TRPBF | 16-Lead SOIC (Narrow 0.15 Inch) | ||
| LT1725IGN#PBF | 16-Lead SSOP (Narrow 0.15 Inch) | ||
| LT1725IGN#TRPBF | 16-Lead SSOP (Narrow 0.15 Inch) | ||
| LT1725IS | 8-Lead SOIC (Narrow 0.15 Inch) | ||
| LT1725IS#PBF | 16-Lead SOIC (Narrow 0.15 Inch) | ||
| LT1725IS#TRPBF | 16-Lead SOIC (Narrow 0.15 Inch) |
| Part Models | Product Lifecycle | PCN |
|---|---|---|
|
Oct 3, 2024 - 24_0235 (QSOP/SSOP PKG) Migrating Bottom Trace Code Marking to Top Side Laser Marking |
||
| LT1725CGN#PBF | PRODUCTION | |
| LT1725CGN#TRPBF | PRODUCTION | |
| LT1725IGN#PBF | PRODUCTION | |
| LT1725IGN#TRPBF | PRODUCTION | |
|
Oct 11, 2022 - 22_0235 Epoxy Change from Henkel 8290 to 8290A for GN Package |
||
| LT1725CGN#PBF | PRODUCTION | |
| LT1725CGN#TRPBF | PRODUCTION | |
| LT1725IGN#PBF | PRODUCTION | |
| LT1725IGN#TRPBF | PRODUCTION | |
|
Apr 6, 2022 - 22_0066 Laser Top Mark for 16QSOP Assembled in ADPG [PNG] |
||
| LT1725CGN#PBF | PRODUCTION | |
| LT1725CGN#TRPBF | PRODUCTION | |
| LT1725IGN#PBF | PRODUCTION | |
| LT1725IGN#TRPBF | PRODUCTION | |
|
Oct 24, 2024 - 24_0246 Migrating Bottom Trace Code Marking to Top Side Laser Marking for SOIC_N Package |
||
| LT1725CS#PBF | PRODUCTION | |
| LT1725CS#TRPBF | PRODUCTION | |
| LT1725IS | ||
| LT1725IS#PBF | PRODUCTION | |
| LT1725IS#TRPBF | PRODUCTION | |
|
Oct 12, 2022 - 22_0252 Epoxy Change from Henkel 8290 to 8290A for 16-Lead SOIC Package |
||
| LT1725CS#PBF | PRODUCTION | |
| LT1725CS#TRPBF | PRODUCTION | |
| LT1725IS | ||
| LT1725IS#PBF | PRODUCTION | |
| LT1725IS#TRPBF | PRODUCTION | |
|
Aug 6, 2022 - 22_0173 Laser Top Mark Conversion for SOICN14 and SOICN16 Packages Assembled on ADPG [PNG] |
||
| LT1725CS#PBF | PRODUCTION | |
| LT1725CS#TRPBF | PRODUCTION | |
| LT1725IS | ||
| LT1725IS#PBF | PRODUCTION | |
| LT1725IS#TRPBF | PRODUCTION | |
|
May 29, 2025 - 25_0024 Carsem SnPb Packaging End of Life |
||
| LT1725IS | ||
This is the most up-to-date revision of the Data Sheet.
Software Resources
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Tools & Simulations
LTspice
Models for the following parts are available in LTspice:
- LT1725
LTspice® is a powerful, fast and free simulation software, schematic capture and waveform viewer with enhancements and models for improving the simulation of analog circuits.
Evaluation Kits
LT1725CGN | Isolated Forward Converter, VIN=36V to 72V, VOUT=3.3V@30A
Resources
LT1725CGN | Isolated Forward Converter, VIN=36V to 72V, VOUT=5V@20A
Resources
LT1725CGN | Isolated Forward Converter, VIN=36V to 72V, VOUT=12V@12A
Resources
LT1725IGN | 48VIN to 5VOUT 2A Module, Isolated Flyback, 1x2 Footprint
Resources
LT1725IGN | 48VIN to 3.3V/3A, 10W Module, Isolated Flyback, 1x2 Footprint
Resources
LT1725CGN | Low Cost, High Efficiency Synchronous Forward Converter without Optoisolator, +VIN = 36V to 72V, +VOUT = 2.5V/3.3V at 10A
Resources
LT1725CGN LTC1773EMS | Telecom Input, Isolated 3 Output DC/DC Converter, +36V to +72V Input, VOUT = 5V/1A, 3.3V/5A, 2.5V/4A
Resources
LT1725CGN | Synchronous Flyback Converter, 36V to 72VIN, to 3.3V @ 3.5A, 350mA Input Current
Resources
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