The FAN7688 is an advanced Pulse Frequency Modulated (PFM) controller for LLC resonant converters with Synchronous Rectification (SR) that offers best in class efficiency for isolated DC/DC converters. It employs a current mode control technique based on a charge control, where the triangular waveform from the oscillator is combined with the integrated switch current information to determine the switching frequency. This provides a better control-to-output transfer function of the power stage simplifying the feedback loop design while allowing true input power limit capability. Closed-loop soft-start prevents saturation of the error amplifier and allows monotonic rising of the output voltage regardless of load condition. A dual edge tracking adaptive dead time control minimizes the body diode conduction time thus maximizing efficiency.
●Features
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● Secondary Side PFM Controller for LLC Resonant Converter with Synchronous Rectifier Control
● Charge Current Control for Better Transient Response and Easy Feedback Loop Design
● Adaptive Synchronous Rectification Control with Dual Edge Tracking
● Closed Loop Soft-Start for Monotonic Rising Output
● Wide Operating Frequency (39 kHz ~ 690 kHz)
● Green Functions to Improve Light-Load Efficiency - Symmetric PWM Control at Light-Load to Limit the Switching Frequency while Reducing Switching Losses - Disabling SR at Light-Load Condition
● Protection Functions with Auto-Restart - Over-Current Protection (OCP) - Output Short Protection (OSP) - NON Zero-Voltage Switching Prevention (NZS) by Compensation Cutback (Frequency Shift) - Power Limit by Compensation Cutback (Frequency Shift) - Overload Protection (OLP) with Programmable Shutdown Delay Time - Over-Temperature Protection (OTP)
● Programmable Dead Times for Primary Side Switches and Secondary Side Synchronous Rectifiers
● VDD Under-Voltage Lockout (UVLO)
● Wide Operating Temperature Range -40°C to +125°C
