100Vin, 5W out regulator uses primary-side control


  • 5.5V to 100V Input Voltage Range
  • 450mA, 150V Internal DMOS Power Switch
  • Up to 5W of Output Power
  • Low Quiescent Current:
     70μA in Sleep Mode
     280μA in Active Mode
  • Boundary Mode Operation at Heavy Load
  • Low-Ripple Burst Mode® Operation at Light Load
  • Minimum Load <0.5% (Typ) of Full Output
  • VOUT Set with a Single External Resistor
  • No Transformer Third Winding or Op to-Isolator
  • Required for Regulation
  • Accurate EN/UVLO Threshold and Hysteresis
  • Internal Compensation and Soft-Start
  • 5-Lead TSOT-23 Package

Typical Application

100Vin, 5W out regulator uses primary-side control


The LT8303 is a micro power high voltage isolated fly back converter. By sampling the isolated output voltage directly from the primary-side fly back waveform, the part requires no third winding or op to-isolator for regulation. The output voltage is programmed with a single external resistor. Internal compensation and soft-start further reduce external component count. Boundary mode operation provides a small magnetic solution with excellent load regulation. Low ripple Burst Mode operation maintains high efficiency at light load while minimizing the output voltage ripple. A 450mA, 150V DMOS power switch is integrated along with all high voltage circuitry and control logic into a 5-lead thin SOT™ package.
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