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reference designLT3574

Analog Devices LT3574

Isolated Flyback Converter Without an Opto-Coupler

Overview

TopologyFlyback Converter
Input voltage12 V
Switching frequency1000 kHz
Output 13.3 V / 0.5 A

Description

The LT®3574 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 theprimary 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 withimproved 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.

Features

  • 3V to 40V Input Voltage Range
  • 0.65A, 60V Integrated NPN Power Switch
  • Boundary Mode Operation
  • No Transformer Third Winding orOpto-Isolator Required for Regulation
  • Improved Primary-Side Winding FeedbackLoad Regulation
  • VOUT Set with Two External Resistors
  • BIAS Pin for Internal Bias Supply and PowerNPN Driver
  • Programmable Soft-Start
  • Programmable Power Switch Current Limit
  • 16-Lead MSOP PackageREMARKS:-REFERTable 5.Predesigned Transformers-Typical Specifications Unless Otherwise NotedPage no 11

Typical applications

  • Industrial, Automotive and Medical Isolated

More information

Products

Order Code
Data­sheet
Simu­lation
Downloads
Status
Product series
VIN
VOut1(V)
IOut1(A)
Vaux(V)
L(µH)
n
ISAT(A)
LS(µH)
VT(V (AC))
Size
IC Reference
SamplesAvailability & Sample
750311304
SPECWE-FB Flyback Transformer suitable for LT3573/ LT3574/ LT3575/ LT3748, 36 V (DC), 5 V
Simu­lation
Availability
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Status Activei| Production is active. Expected lifetime: >10 years.
Product seriesWE-FB Flyback Transformer suitable for LT3573/ LT3574/ LT3575/ LT3748
Input Voltage 36 V (DC)
Output Voltage 15 V
Output Current 13 A
Auxiliary Voltage10 V
Inductance50 µH
Turns Ratio4:1:1.5 
Saturation Current2.4 A
Leakage Inductance1.5 µH
Insulation Test Voltage1500 V (AC)
SizeEP10 
IC ReferenceLT3574 & LT3575 
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