LT8311 - Synchronous Rectifier Controller with Opto-Coupler Driver for Forward Converters


  • Wide Input Supply Range: 3.7V to 30V
  • Preactive Mode:
  • No Pulse Transformer Required
  • DCM Operation at Light Load
  • SYNC Mode:
  • FCM or DCM Operation at Light Load
  • Achieves Highest Efficiency
  • 1.5% Feedback Voltage Reference
  • 10mA Opto-Coupler Driver
  • Output Power Good Indicator
  • Integrated Soft-Start Function

Typical Application

LT8311 Typical Application


The LT®8311 is used on the secondary side of a forward converter to provide synchronous MOSFET control and output voltage feedback through an opto-coupler. The LT8311’s unique preactive mode allows control of the secondary-side MOSFETs without requiring a traditional pulse transformer for primary- to secondary-side communication. In preactive mode, the output inductor current operates in discontinuous conduction mode (DCM) at light load. If forced continuous mode (FCM) operation is desired at light load, the LT8311 can, alternatively, be used in SYNC mode, where a pulse transformer is required to send synchronous control signals from the primary-side IC to the LT8311.

The LT8311 offers a full featured opto-coupler controller, incorporating a 1.5% reference, a transconductance error amplifier and a 10mA opto-driver. Power good monitoring and output soft-start/overshoot control are also included. The LT8311 is available in a 16-lead FE package with pins removed for high voltage spacing requirements.


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
LT8311EFE#PBF TSSOP-20 FE E 05-08-1924 Yes
LT8311EFE#TRPBF TSSOP-20 FE E 05-08-1924 Yes
LT8311HFE#PBF TSSOP-20 FE H 05-08-1924 Yes
LT8311HFE#TRPBF TSSOP-20 FE H 05-08-1924 Yes
LT8311IFE#PBF TSSOP-20 FE I 05-08-1924 Yes
LT8311IFE#TRPBF TSSOP-20 FE I 05-08-1924 Yes
LT8311MPFE#PBF TSSOP-20 FE MP 05-08-1924 Yes
LT8311MPFE#TRPBF TSSOP-20 FE MP 05-08-1924 Yes

LT8311 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
LT8311EFE#PBF TSSOP-20 E $4.37 $3.06 Yes
LT8311EFE#TRPBF TSSOP-20 E $3.12 Yes
LT8311HFE#PBF TSSOP-20 H $5.22 $3.65 Yes
LT8311HFE#TRPBF TSSOP-20 H $3.71 Yes
LT8311IFE#PBF TSSOP-20 I $4.79 $3.35 Yes
LT8311IFE#TRPBF TSSOP-20 I $3.41 Yes
LT8311MPFE#PBF TSSOP-20 MP $12.94 $9.06 Yes
LT8311MPFE#TRPBF TSSOP-20 MP $9.12 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
DC1929A LT3752EFE-1/ LT8311EFE Demo Board | 150V ≤ VIN ≤ 400V, VOUT = 12V @ 16.7A $300.00
DC1994A LT3752EFE/LT8311EFE Isolated Demo Board | 18V ≤ VIN ≤ 72V; VOUT: 12V @ 12A $300.00
DC2015A LT8310EFE/LT8311EFE Isolated Demo Board | 36V ≤ VIN ≤ 72V; VOUT = 12V @ 12A $300.00
DC2175A LT3752IFE/LT8311IFE Demo Board | Forward Converter with Sync Rectification, 9V ≤ VIN ≤ 36V; Vout = 12V @ 13A $300.00
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Click here to view our complete list of demo boards


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