Fairchild Semiconductor – FSL306 and FSL336: 650V Green Mode Buck Switches Offer the Highest Power Efficiency


The FSL306LRN and FSL336LRN integrated pulse width modulator (PWM) and senseFET are specifically designed for high performance offline buck, buck-boost, and non-isolation flyback switched mode power supplies (SMPS) with minimal external components. These devices integrate a high voltage power regulator that enables operation without auxiliary bias winding. An internal transconductance amplifier reduces external components for the feedback compensation circuit. These devices also offer burst-mode operation with the low available operating current (250µA) that helps to reduce stand-by mode power consumption for increased energy efficiency.


  • 50kHz fixed operating frequency
  • Frequency modulation for attenuating EMI
  • 250µA operating current
  • Built-in soft start and start-up circuit
  • Built-in transconductance (error) amplifier
  • Adjustable peak current limit
  • 25mW no-load power consumption
  • Pulse-by-pulse current limiting
  • OLP, OVP, thermal shutdown (TSD)
  • Feedback open loop protection (FB_OLP)
  • Abnormal overcurrent protection (AOCP) (FSL306LRN)
  • 1k MSRP: $0.83/$0.85 US