ON Semiconductor


FSL138MRT Green-Mode Fairchild Power Switch (FPS™) for High Input Voltage

Topology: Flyback
Input Voltage (min.): 80.00 V
Input Voltage (max.): 310.00 V
Switching Frequency (min.): 61.00 kHz
Switching Frequency (max.): 73.00 kHz
Output 1: 50.00 V / 2.000 A
Output 2: 62.00 V / 1.400 A

Original publication on 2012-05-29, revision 1.0.0


The FSL138MRT is an integrated Pulse Width Modulation (PWM) controller and SenseFET specifically designed for offline Switched-Mode Power Supplies (SMPS) with minimal external components. The PWM controller includes an integrated fixed-frequency oscillator, Under-Voltage Lockout (UVLO), Leading-Edge Blanking (LEB), optimized gate driver, internal soft-start, temperature-compensated precise current sources for loop compensation, and self-protection circuitry. Compared with a discrete MOSFET and PWM controller solution, the FSL138MRT can reduce total cost, component count, size, and weight; while simultaneously increasing efficiency, productivity, and system reliability. This device provides a basic platform suited for cost-effective design of a flyback converter.


  • Internal Avalanched-Rugged 800V SenseFET
  • Advanced Soft Burst-Mode Operation for Low Standby Power and Low Audible Noise
  • Under 40mW Standby Power Consumption at 265VAC and No-load Condition
  • Random Frequency Fluctuation for Low EMI
  • Pulse-by-Pulse Current Limit
  • Various Protection Functions: Overload Protection (OLP), Over-Voltage Protection (OVP), Abnormal Over-Current Protection (AOCP), Internal Thermal Shutdown (TSD) with Hysteresis and Under-Voltage Lockout (UVLO) with Hysteresis
  • Low Operating Current (0.4mA) in Burst Mode
  • Internal Startup Circuit
  • Built-in Soft-Start: 15ms
  • Auto-Restart Mode


  Order Code SPEC Product series L
RDC typ.
Montageart Samples
750311795 PDF Common Mode Choke
750313584 PDF Flyback with PFC. Single and 4 channel LED Driver. 80-310VACin, 100W out.
750313579 PDF Flyback with PFC. Single and 4 channel LED Driver. 80-310VACin, 100W out.
744028004 PDF WE-TPC SMT Tiny Power Inductor 4.7 0.85 0.7 265 70 SMT

Other applications and Würth Elektronik products for this IC

  • FSL138MRT
    Topology: Other, Switching Frequency (min.): 61.00 kHz, Switching Frequency (max.): 73.00 kHz