Features and Benefits
- 3V to 40V Input Voltage Range
- 0.65A, 60V Integrated NPN Power Switch
- Boundary Mode Operation
- No Transformer Third Winding or Opto-Isolator Required for Regulation
- Improved Primary-Side Winding Feedback Load Regulation
- VOUT Set with Two External Resistors
- BIAS Pin for Internal Bias Supply and Power NPN Driver
- Programmable Soft-Start
- Programmable Power Switch Current Limit
- 16-Lead MSOP Package
The LT3574 is a monolithic switching regulator specifically designed for the isolated flyback topology. No third winding or opto-isolator is required for regulation. The part senses the isolated output voltage directly from the primary side flyback waveform. A 0.65A, 60V NPN power switch is integrated along with all control logic into a 16‑lead MSOP package.
The LT3574 operates with input supply voltages from 3V to 40V, and can deliver output power up to 3W with no external power switch. The LT3574 utilizes boundary mode operation to provide a small magnetic solution with improved load regulation.
The output voltage is easily set with two external resistors and the transformer turns ratio. Off-the-shelf transformers are available for many applications.
- Industrial, Automotive and Medical Isolated Power Supplies
Product Lifecycle Production
At least one model within this product family is in production and available for purchase. The product is appropriate for new designs but newer alternatives may exist.
Evaluation Kits (1)
Demonstration circuit 1636A is an isolated flyback converter featuring the LT3574. This demo circuit is designed for a 5.0V output from a 10V to 30V input. The maximum output current is 0.5A when the input voltage is higher than 20V. No third winding or opto-isolator is required for regulation. The part senses the isolated output voltage directly from the primary-side flyback waveform. The LT3574 operates with input supply voltages from 3V to 40V, and can deliver an output power up to 3W with no external power switch. The LT3574 utilizes boundary mode operation to provide a small magnetic solution with improved load regulation.
Documentation & Resources
R530 Reliability Data3/26/2018
DC1636A - Demo Manual9/24/2013
48V No-Opto Isolated Applications12/21/2010
Isolated Power Your Way1/21/2014
Tools & Simulations
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.
To launch ready-to-run LTspice demonstration circuits for this part:
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Step 2: Click on the link in the section below to download a demonstration circuit.
Step 3: If LTspice does not automatically open after clicking the link below, you can instead run the simulation by right clicking on the link and selecting “Save Target As.” After saving the file to your computer, start LTspice and open the demonstration circuit by selecting ‘Open’ from the ‘File’ menu.
Models for the following parts are available in LTspice:
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Pricing displayed is based on 1-piece. The USA list pricing shown is for budgetary use only, shown in United States dollars (FOB USA per unit), and is subject to change. International prices may vary due to local duties, taxes, fees and exchange rates.