Isolated Secondary Synchronous Rectifier Controller

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.

Applications

* 48V Input Isolated DC/DC Converters

* Isolated Telecommunication Power Systems

* Distributed Power Step-Down Converters

* Industrial Control Systems

* Automotive and Heavy Equipment

* 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