FTM Board Club
38 V, 5 W synchronous iso-buck converter evaluation board with dual isolated output based on the A6986I

The STEVAL-A6986IV1 evaluation board is based on ST A6986I automotive 38 V, 5 W synchronous iso-buck converter for isolated applications. The primary output voltage can be accurately adjusted, whereas the isolated secondary output is generated by a transformer. No optocoupler is required.

The primary sink capability (typ. 1.9 A) allows a proper 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 and the device operates in forced PWM. 

The 300 ns blanking time filters oscillations generated by the transformer leakage inductance and makes the solution more robust.

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

The evaluation board generates two isolated voltages (positive around 18 V and negative between 4 V and 5 V), especially suitable for supplying IGBT/SiC MOSFET gate driver. A simple bypass enables the supply of a single isolated voltage.

  • AEC-Q100 qualified
  • Operating temperature range: -40 °C to 135 °C for Tj
  • Designed for iso-buck topology
  • 4 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