LT3573 - Isolated Flyback Converter without an Opto-Coupler

Features

• Click Here for LT3573 Evaluation Kit
• 3V to 40V Input Voltage Range
• 1.25A, 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
• V_OUT Set with Two External Resistors
• BIAS Pin for Internal Bias Supply and Power NPN Driver
• Programmable Soft-Start
• Programmable Power Switch Current Limit
• Thermally Enhanced 16-Lead MSOP

Typical Application

Description

The LT3573 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 1.25A, 60V NPN power switch is integrated along with all control logic into a 16‑lead MSOP package.

The LT3573 operates with input supply voltages from 3V to 40V, and can deliver output power up to 7W with no external power devices.The LT3573 utilizes boundary mode operation to provide a small magnetic solution with improved load regulation.

Packaging

MS-16

Order Info

• Part numbers ending in PBF are lead free. Please contact LTC marketing for information on lead based finish parts.
• Part numbers containing TR or TRM are shipped in tape and reel or 500 unit mini tape and reel, respectively
• Please refer to our general ordering information or the product datasheet for more details

Package Variations and Pricing

Part Number	Package	Pins	Temp	Price (1-99)	Price (1k)*	RoHS Data
LT3573EMSE#PBF	MSOP	16	E	$3.94	$2.76	View
LT3573EMSE#TRPBF	MSOP	16	E		$2.82	View
LT3573IMSE#PBF	MSOP	16	I	$4.46	$3.12	View
LT3573IMSE#TRPBF	MSOP	16	I		$3.18	View
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^* The USA list pricing shown is for BUDGETARY USE ONLY, shown in United States dollars (FOB USA per unit for the stated volume), and is subject to change. International prices may differ due to local duties, taxes, fees and exchange rates. For volume-specific price or delivery quotes, please contact your local Linear Technology sales office or authorized distributor.

Evaluation Kits

Part Number	Description	Price
DC1228A	LT3573EMSE | 24Vin to 5Vout at 1A Isolated Monolithic Flyback Converter	$100.00
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Applications

• Industrial, Automotive and Medical Isolated Power Supplies

Simulate

LTSpice IV is a powerful FREE circuit simulator and schematic capture program, providing macro models for 80% of Linear Technology's switching regulators, over 200 op amp models, as well as resistors, transistors and MOSFET models.

• Step 1. If you do not already have a copy of LTSpice IV, click here to download and install LTSpice / SwitcherCAD III
  
  
• Step 2. Once LTSpice is installed, click here for a ready to run  demonstration circuit of the LT3573.
  
  
• Step 3. If LTspice IV does not automatically open after clicking the above link, 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 demonstartion circuit by selecting "Open" from the "File" menu.

For our complete list of hundreds of ready to run demo circuits, visit our LTspice IV Demo Circuits Collection