STEVAL-L6986IV1 Synchronous Iso-Buck Converter Evaluation Board

STEVAL-L6986IV1 Synchronous Iso-Buck Converter Evaluation Board

STMicroelectronics’ evaluation board with dual isolated output is based on the L6986I

STMicroelectronics’ 38 V, 5 W synchronous iso-buck converter evaluation board generates two isolated voltages (approx. +18 V and between -4 V and -5 V), suitable for supplying IGBT/SiC MOSFET gate drivers or a single isolated voltage using a simple bypass. The board features the L6986I switching converter allowing a fine and adjustable primary output voltage and an isolated secondary output generated using a transformer.

The primary sink capability (typ. 1.9 A) allows appropriate energy transfer to the secondary side and enables a tracked soft-start of the secondary output. The control loop is based on a peak current mode architecture with the device operating in forced PWM. The 300 ns blanking time filters oscillations generated by the transformer leakage inductance and renders the solution more robust.

Pulse-by-pulse current sensing on both power elements implements effective constant current protection on the primary side. At the same time, the secondary output is protected against short-circuit events because of the primary reverse current limit. The secondary voltage is stabilized over current with a power transistor and a shunt voltage reference (TL431).


  • Designed for iso-buck topology
  • 4 V to 38 V operating input voltage
  • Primary output voltage regulation/no optocoupler required
  • 1.9 A typical sink peak primary current capability
  • Peak current mode architecture in forced PWM operation
  • 300 ns blanking time
  • 8 µA IQ-SHTDWN
  • Adjustable fSW and synchronization
  • Embedded primary output voltage supervisor
  • Adjustable soft-start time
  • Internal primary current limiting
  • Overvoltage protection
  • RDS(ON) HS = 180 mΩ, RDS(ON) LS = 150 mΩ
  • Thermal shutdown

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