LTC3766 - High Efficiency, Secondary-Side Synchronous Forward Controller


  • Direct Flux Limit™ Guarantees No Saturation
  • Fast and Accurate Average Current Limit
  • Clean Start-Up Into Pre-Biased Output
  • Secondary-Side Control for Fast Transient Response
  • Simple, Self-Starting Architecture
  • Synchronous MOSFET Reverse Current Limit
  • PolyPhase® Operation Eases High-Power Design
  • True Remote Sense Differential Amplifier
  • Remote Sense Reverse Protection
  • High Voltage Linear Regulator Controller
  • Internal LDO Powers Gate Drive from VOUT
  • Overtemperature/Overvoltage Protection
  • Low Profile 4mm × 5mm QFN and Narrow 28-Lead SSOP Packages

Typical Application

LTC3766 Typical Application


The LTC®3766 is a PolyPhase-capable secondary-side controller for synchronous forward converters. When used in conjunction with the LTC3765 active-clamp forward controller and gate driver, the part creates a complete isolated power supply that combines the power of multiphase operation with the speed of secondary-side control.

The LTC3766 has been designed to simplify the design of active clamp forward converters. Working in concert with the LTC3765, the LTC3766 forms a robust, self-starting converter that eliminates the need for the separate bias regulator that is commonly used in secondary-side control applications. A precision current-limit coupled with clean start-up into a pre-biased load make the LTC3766 an excellent choice for high-power battery charger applications.

The LTC3766 provides extensive remote sensing and output protection features, while Direct Flux Limit guarantees no transformer saturation without compromising transient response. A linear regulator controller and internal bypass LDO are also provided to simplify the generation of the secondary-side bias voltage.


CAD Symbols and Footprints: The downloadable Zip file below contains the schematic symbol and PCB footprints.

For complete and up to date package information and drawings, please refer to our packaging page

Part Number Package Code Temp Package
LTC3766EGN#PBF SSOP-28 GN E 05-08-1641 (GN28) Yes
LTC3766EGN#TRPBF SSOP-28 GN E 05-08-1641 (GN28) Yes
LTC3766EUFD#PBF 4x5 QFN-28 UFD E 05-08-1712 Yes
LTC3766EUFD#TRPBF 4x5 QFN-28 UFD E 05-08-1712 Yes
LTC3766HGN#PBF SSOP-28 GN H 05-08-1641 (GN28) Yes
LTC3766HGN#TRPBF SSOP-28 GN H 05-08-1641 (GN28) Yes
LTC3766HUFD#PBF 4x5 QFN-28 UFD H 05-08-1712 Yes
LTC3766HUFD#TRPBF 4x5 QFN-28 UFD H 05-08-1712 Yes
LTC3766IGN#PBF SSOP-28 GN I 05-08-1641 (GN28) Yes
LTC3766IGN#TRPBF SSOP-28 GN I 05-08-1641 (GN28) Yes
LTC3766IUFD#PBF 4x5 QFN-28 UFD I 05-08-1712 Yes
LTC3766IUFD#TRPBF 4x5 QFN-28 UFD I 05-08-1712 Yes
LTC3766MPGN#PBF SSOP-28 GN MP 05-08-1641 (GN28) Yes
LTC3766MPGN#TRPBF SSOP-28 GN MP 05-08-1641 (GN28) Yes
LTC3766MPUFD#PBF 4x5 QFN-28 UFD MP 05-08-1712 Yes
LTC3766MPUFD#TRPBF 4x5 QFN-28 UFD MP 05-08-1712 Yes

LTC3766 Package Drawing
LTC3766 Package Drawing

Order Info

  • Part numbers ending in PBF are lead free. Solder plated terminal finish (SnPb) versions are non-standard and special terms and conditions and pricing applies if available. Please contact LTC marketing for information.
  • 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 Temp Price
LTC3766EGN#PBF SSOP-28 E $5.54 $3.88 Yes
LTC3766EGN#TRPBF SSOP-28 E $3.94 Yes
LTC3766EUFD#PBF 4x5 QFN-28 E $5.54 $3.88 Yes
LTC3766EUFD#TRPBF 4x5 QFN-28 E $3.94 Yes
LTC3766HGN#PBF SSOP-28 H $6.54 $4.58 Yes
LTC3766HGN#TRPBF SSOP-28 H $4.64 Yes
LTC3766HUFD#PBF 4x5 QFN-28 H $6.54 $4.58 Yes
LTC3766HUFD#TRPBF 4x5 QFN-28 H $4.64 Yes
LTC3766IGN#PBF SSOP-28 I $6.11 $4.28 Yes
LTC3766IGN#TRPBF SSOP-28 I $4.34 Yes
LTC3766IUFD#PBF 4x5 QFN-28 I $6.11 $4.28 Yes
LTC3766IUFD#TRPBF 4x5 QFN-28 I $4.34 Yes
LTC3766MPGN#PBF SSOP-28 MP $16.51 $11.56 Yes
LTC3766MPGN#TRPBF SSOP-28 MP $11.62 Yes
LTC3766MPUFD#PBF 4x5 QFN-28 MP $16.51 $11.56 Yes
LTC3766MPUFD#TRPBF 4x5 QFN-28 MP $11.62 Yes
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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.

Demo Boards

Linear Technology offers many demo boards free of charge to qualified customers. Contact your local sales office or distributor to inquire about a demo board. Certain demo boards are also available for sale via credit card on this website. Demo boards are for evaluation purposes only. It remains the customer’s responsibility to verify proper and reliable operation in the actual end application.

Part Number Description Price Documentation
DC1739A-B LTC3765EMSE/LTC3766EGN Isolated Demo Board | Forward Converter, 18V ≤ VIN ≤ 72V; VOUT = 12V @ 12.5A $300.00
DC1739B-C LTC3765EMSE/LTC3766EGN Isolated Demo Board | Forward Converter, 9V ≤ VIN ≤ 36V; VOUT = 12V @ 10A $300.00
DC2199A-A LTC3765EMSE/LTC3766EGN Isolated Demo Board | Forward Converter, 36V ≤ VIN ≤ 60V; VOUT = 12V @ 30A $300.00
DC2199A-B LTC3765EMSE/LTC3766EGN Isolated Demo Board | Forward Converter with Sync Rectification, 36V ≤ VIN ≤ 60V; VOUT = 24V @ 15A $300.00
DC2199B-C LTC3765EMSE/LTC3766EGN Isolated Demo Board | Forward Converter with Sync Rectification, 36V ≤ VIN ≤ 60V; VOUT = 56V @ 5.4A $300.00
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Click here to view our complete list of demo boards


  • Isolated 48V Telecommunication Systems
  • Isolated Battery Chargers
  • Automotive and Military Systems
  • Industrial, Avionics and Heavy Equipment

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