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FAN6208 —Secondary-Side Synchronous Rectifier Controller for LLC Topology
October 2014
FAN6208
Secondary-Side Synchronous Rectifier Controller for
LLC Topology
Features
Specialized SR Controller for LLC or LC Resonant
Converters
Secondary-Side Timing Detection with Timing
Estimator
Gate-Shrink Function to Prevent Shoot-Through
During Load and Line Transient
Green-Mode Function for Higher Efficiency at Light-
Load Condition
Programmable Dead Time between Primary-Side
Gate Drive Signal and SR Drive Signal
Advanced Output-Short / Overload Protection
Based on the Feedback Information
Internal Over-Temperature Protection (OTP)
V
DD
Pin Over-Voltage Protection (OVP)
Description
FAN6208 is a synchronous rectification (SR) controller
for isolated LLC or LC resonant converters that can
drive two individual SR MOSFETs emulating the
behavior of rectifier diodes. FAN6208 measures the SR
conduction time of each switching cycle by monitoring
the drain-to-source voltage of each SR and determines
the optimal timing of the SR gate drive. FAN6208 uses
the change of opto-coupler diode current to adaptively
shrink the duration of SR gate drive signals during load
transients to prevent shoot-through. To improve light-
load efficiency, Green-Mode operation is employed,
which disables the SR drive signals, minimizing gate
drive power consumption at light-load condition.
Optimal timing circuits and protection functions are
integrated in an 8-pin SOP package, which allows high-
efficiency power supply design with fewer components.
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