STMicroelectronics STEVAL-L6986IV1

Overview

STEVAL-L6986IV1 from STMicroelectronics is an evaluation board based on the L6986I 38 V, 5 W synchronous iso-buck DC-DC converter IC, designed for isolated gate driver power supplies in IGBT/SiC MOSFET applications. It delivers dual isolated outputs (≈+18 V and −4.5 V), operates from 4–38 V input, supports forced PWM with 300 ns current-sense blanking, and embeds primary-side voltage supervision and thermal shutdown.

For engineers reviewing the STEVAL-L6986IV1 datasheet, STEVAL-L6986IV1 schematic, STEVAL-L6986IV1 application notes, or STEVAL-L6986IV1 alternative evaluation boards, this board enables rapid validation of transformer-coupled, optocoupler-free isolated bias supply designs with adjustable positive/negative output voltages and robust short-circuit protection on the secondary side.

Technical Context

The board implements an isolated buck (iso-buck) topology using the L6986I controller, which regulates the primary-side output voltage directly-eliminating need for optocouplers or secondary-side feedback. Peak current mode control with 300 ns blanking time suppresses leakage inductance ringing, while pulse-by-pulse sensing on high- and low-side FETs enables precise primary current limiting (1.9 A sink peak) and reverse-current–based secondary short-circuit protection.

Secondary regulation uses a TL431AIL3T shunt reference and discrete transistor to stabilize output without auxiliary winding sensing. The board supports dual isolated outputs by default (+18 V and −4.5 V), with resistor-divider (R12/R13) adjustment for positive voltage and Zener replacement (D3) for negative voltage tuning-enabling flexible gate-driver bias configurations across motor drives and power converters.

Key Specifications

Availability

STEVAL-L6986IV1 is available at Aetrix Electronics and suitable for IGBT/SiC gate driver biasing, industrial motor control power stages, and isolated auxiliary supply design requiring stable component supply and fast prototyping turnaround.

Supply support for STEVAL-L6986IV1 includes scheduled delivery planning, volume procurement assistance, BOM continuity management, traceable sourcing, and lifecycle availability coordination for OEM customers, industrial embedded developers, connected-device designers, and electronics production programs.

Manufacturer

STMicroelectronics is a global semiconductor leader headquartered in Geneva, designing and manufacturing microcontrollers, power ICs, analog chips, and sensors for industrial, automotive, and consumer applications.

The STEVAL-L6986IV1 belongs to ST's power conversion evaluation platform family, engineered specifically to accelerate development of isolated, optocoupler-free bias supplies for high-reliability power electronics systems.

FAQ

What is the purpose of the 300 ns blanking time on STEVAL-L6986IV1?

The 300 ns blanking time disables current sensing immediately after switch turn-on to ignore voltage spikes caused by transformer leakage inductance. This prevents false overcurrent triggering and improves system robustness during hard-switching transitions in iso-buck topologies-critical for reliable gate driver supply operation under dynamic load conditions.

Can STEVAL-L6986IV1 generate only a single isolated output?

Yes. By removing diode D3 and replacing capacitor C12 with a 0 Ω resistor, the board delivers only the positive isolated output (VISO+). This configuration simplifies testing of single-rail gate drivers or auxiliary supplies while retaining full primary-side regulation and protection functionality.

How is secondary-side short-circuit protection implemented without direct sensing?

Secondary short-circuit protection is achieved indirectly via primary reverse current detection. When secondary output is shorted, reflected current reversal on the primary side triggers the L6986I's built-in reverse-current limit, forcing shutdown-eliminating need for secondary-side current sensors or optocouplers while maintaining isolation integrity.

What components enable adjustable isolated output voltages?

Positive output voltage is adjusted via resistor divider R12/R13 (equation: VISO+ = 2.49 × (R12/R13 + 1)). Negative output voltage is tuned by replacing Zener diode D3 with a user-selected Zener value. Fine-tuning of R11 may be needed after either modification to maintain optimal regulation stability.