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ADI Power by Linear LT3574

Isolated Flyback Converter Without an Opto-Coupler

Overview

TopologyFlyback Converter
Input voltage3-40 V
Switching frequency1000 kHz

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

Products

Order Code Data­sheet Downloads Product seriesVinVOut1
(V)
IOut1
(A)
VOut2
(V)
IOut2
(A)
L1
(µH)
nISAT 1
(A)
LSmin.
(µH)
VT
(V (AC))
SizeIC Reference Samples
750311307SPEC
8 files WE-FB Flyback Transformer suitable for LT3573/ LT3574/ LT3575/ LT3748 9 - 30 V (DC) 24 0.5 100 2 : 1 1.9 2 1500 EP10 LT3574 & LT3575
750311308SPEC
8 files WE-FB Flyback Transformer suitable for LT3573/ LT3574/ LT3575/ LT3748 9 - 30 V (DC) 24 0.5 100 1 : 1 2.1 2.1 1500 EP10 LT3574 & LT3575
750311304SPEC
8 files WE-FB Flyback Transformer suitable for LT3573/ LT3574/ LT3575/ LT3748 9 - 30 V (DC) 5 3 50 4 : 1 2.4 0.85 1500 EP10 LT3574 & LT3575
750310564SPEC
8 files WE-FB Flyback Transformer suitable for LT3573/ LT3574/ LT3575/ LT3748 12 - 30 V (DC) 5 1 5 1 63 3 : 1 1.45 0.6 1500 EP10 LT3574 & LT3573 & LT3575
750370041SPEC
8 files WE-FB Flyback Transformer suitable for LT3573/ LT3574/ LT3575/ LT3748 18 - 30 V (DC) 5 1 50 3 : 1 1.6 0.45 1500 EP7 LT3574 & LT3573
750370040SPEC
8 files WE-FB Flyback Transformer suitable for LT3573/ LT3574/ LT3575/ LT3748 18 - 30 V (DC) 5 1 30 3 : 1 1.7 1 1500 EP7 LT3574 & LT3573
750370047SPEC
8 files WE-FB Flyback Transformer suitable for LT3573/ LT3574/ LT3575/ LT3748 18 - 30 V (DC) 5 1 30 3 : 1 1.7 1 1500 EP7 LT3574 & LT3573
Samples
Order Code Data­sheet Downloads Product seriesVinVOut1
(V)
IOut1
(A)
VOut2
(V)
IOut2
(A)
L1
(µH)
nISAT 1
(A)
LSmin.
(µH)
VT
(V (AC))
SizeIC Reference Samples