Features and Benefits
- 5V to 100V Input Voltage Range
- 1.9A Average Gate Drive Source and Sink Current
- Boundary Mode Operation
- No Transformer Third Winding or Opto-Isolator Required for Regulation
- Primary-Side Winding Feedback Load Regulation
- VOUT Set with Two External Resistors
- INTVCC Pin for Control of Gate Driver Voltage
- Programmable Soft Start
- Programmable Undervoltage Lockout
- Available in MSOP Package
The LT3748 is a switching regulator controller specifically designed for the isolated flyback topology and capable of high power. It drives a low side external N-channel power MOSFET from an internally regulated 7V supply. No third winding or opto-isolator is required for regulation as the part senses the isolated output voltage directly from the primary-side flyback waveform.
The LT3748 utilizes boundary mode to provide a small magnetic solution without compromising load regulation. Operating frequency is set by load current and transformer magnetizing inductance. The gate drive of the LT3748 combined with a suitable external MOSFET allow it to deliver load power up to several tens of watts from input voltages as high as 100V.
The LT3748 is available in a high voltage 16-lead MSOP package with four leads removed.
- Isolated Telecom Converters
- High Power Automotive Supplies
- Isolated Industrial Power Supplies
- Military and High Temperature Applications
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 (4)
Demonstration circuit 1961A features the LT8309, a secondary synchronous driver in an isolated, no optocoupler, flyback converter. It regulates a 12V, 5A output from a 36V to 72V input source. Output regulation is handled on the primary side by the LT3748, a boundary conduction mode flyback controller which senses output voltage directly from the primary, resulting in a simple flyback schematic with no opto-coupler.
Demonstration circuit 1860B is an isolated flyback converter featuring the LT3748. This demo circuit is designed for Power Sourcing Equipment (PSE) applications with a 52.5V output from a 10V to 15V DC input, with nominal input voltage of 12V. The output current is from 0mA to 700mA, and is capable of a maximum short period overload current of 900mA.
The LT3748 is a high input voltage isolated flyback controller operating with input supply voltages from 5V to 100V, and 1.9A average gate drive source and sink current.
Demonstration circuit 1694B is an isolated flyback converter featuring the LT3748. The demo circuit is designed for a 12V output from a 22V to 75V DC input. The output current is up to 2.5A. The part senses the isolated output voltage directly from the primary side flyback waveform during the off time of the power switch. No third winding, opto-coupler, or signal transformer is required for regulation. A minimum load of approximately 2% of maximum load is required on the output to maintain regulation.
Demonstration circuit 1557A is an Non-Opto Isolated Flyback Converter featuring LT3748EMS. It is designed for 12V output from a 30V to 75V DC input. The output current is up to 1A. The part senses the isolated output voltage directly from the primary side flyback waveform during the off time of the power switch. No third winding, opto-coupler or signal transformer is required for regulation. A minimum load of approximately 2% of maximum load is required on the output.
The LT3748EMS is a high input voltage isolated flyback controller operating with input supply voltages from 5V to 100V. The LT3748EMS utilizes boundary mode operation to provide a high efficiency, small size solution with improved load regulation of ±5% over the full line, load and temperature ranges.
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:
Step 1: Download and install LTspice on your computer.
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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