LTC1698 - Isolated Secondary Synchronous Rectifier Controller


  • High Efficiency Over Wide Load Current Range
  • ±0.8% Output Voltage Accuracy
  • Dual N-Channel MOSFET Synchronous Drivers
  • Pulse Transformer Synchronization
  • Optocoupler Feedback Driver
  • Programmable Current Limit Protection
  • ±5% Margin Output Voltage Adjustment
  • Adjustable Overvoltage Fault Protection
  • Power Good Flag
  • Auxiliary 3.3V Logic Supply
  • Available in 16-Lead SSOP and SO Packages

Typical Application

LTC1698 Typical Application


The LTC1698 is a precision secondary-side forward converter controller that synchronously drives external N-channel MOSFETs. It is designed for use with the LT3781 primary-side synchronous forward converter controller to create a completely isolated power supply. The LT3781 synchronizes the LTC1698 through a small pulse transformer and the LTC1698 drives a feedback optocoupler to close the feedback loop. Output accuracy of ±0.8% and high efficiency over a wide range of load currents are obtained.

The LTC1698 provides accurate secondary-side current limit using an external current sense resistor. The input voltage at the MARGIN pin provides ±5% output voltage adjustment. A power good flag and overvoltage input are provided to ensure proper power supply conditions. An auxiliary 3.3V logic supply is included that supplies up to 10mA of output current.


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
LTC1698EGN#PBF SSOP-16 GN E 05-08-1641 (GN16) Yes
LTC1698EGN#TRPBF SSOP-16 GN E 05-08-1641 (GN16) Yes
LTC1698ES#PBF SO-16 S E 05-08-1610 (S16) Yes
LTC1698ES#TRPBF SO-16 S E 05-08-1610 (S16) Yes
LTC1698IGN#PBF SSOP-16 GN I 05-08-1641 (GN16) Yes
LTC1698IGN#TRPBF SSOP-16 GN I 05-08-1641 (GN16) Yes
LTC1698IS#PBF SO-16 S I 05-08-1610 (S16) Yes
LTC1698IS#TRPBF SO-16 S I 05-08-1610 (S16) Yes

LTC1698 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
LTC1698EGN#PBF SSOP-16 E $6.27 $5.30 Yes
LTC1698EGN#TRPBF SSOP-16 E $5.36 Yes
LTC1698ES#PBF SO-16 E $6.33 $5.35 Yes
LTC1698ES#TRPBF SO-16 E $5.41 Yes
LTC1698IGN#PBF SSOP-16 I $6.92 $5.85 Yes
LTC1698IGN#TRPBF SSOP-16 I $5.91 Yes
LTC1698IS#PBF SO-16 I $6.98 $5.90 Yes
LTC1698IS#TRPBF SO-16 I $5.96 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
DC479A LT3781EG, LTC1698EGN, LT1783CS5 | Isolated Synchronous, Forward Converter, Vin=36V-72V, Vout=3.3V @ 15A $75.00
DC617A LT3781EG LTC1698EGN LT1783CS5 | Isolated Synchronous Forward Converter, +Vin = 36V - 72V, +Vout = 2.5V @ 20A, Quarter Brick footprint $75.00
DC759A LT1952EGN, LTC1698EGN | 48Vin to 5V at 20A Converter, +Vin = 36V - 72V, +Vout = +5V at 20A $175.00
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Click here to view our complete list of demo boards


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