STMicroelectronics STEVAL-A6986IV1

Overview

STEVAL-A6986IV1 from STMicroelectronics is an automotive-grade evaluation board based on the A6986I synchronous iso-buck DC-DC converter, designed for isolated gate-driver power supplies in traction inverters and on-board chargers. It delivers dual isolated outputs (≈+18 V and −4.3 V), supports 4–38 V input, operates up to 135 °C junction temperature, and implements peak current mode control with 300 ns blanking time for transformer leakage immunity.

For engineers reviewing the STEVAL-A6986IV1 datasheet, STEVAL-A6986IV1 pinout, STEVAL-A6986IV1 application, or STEVAL-A6986IV1 equivalent, this board enables rapid validation of isolated 5 W power delivery using ST's AEC-Q100-qualified iso-buck topology-especially for IGBT/SiC gate driver biasing under harsh automotive thermal and EMI conditions.

Technical Context

The board implements a primary-side regulated iso-buck architecture where output voltage accuracy is maintained without optocouplers via embedded primary-side voltage supervision and TL431-based secondary shunt regulation. The A6986I controller operates in forced PWM with pulse-by-pulse current sensing on both high-side (R_DS(on) = 180 mΩ) and low-side (R_DS(on) = 150 mΩ) MOSFETs.

Transformer-coupled energy transfer enables dual-polarity isolated outputs; negative rail generation uses a Zener diode (BZT52B4V3), while positive rail adjustment follows V_ISO = 2.49 × (R12 + R13)/R13. Short-circuit protection on the secondary side is enforced by primary reverse-current limiting.

Key Specifications

Availability

STEVAL-A6986IV1 is available at Aetrix Electronics and suitable for electric traction inverters, on-board chargers (OBC), and isolated gate-driver power supplies requiring stable component supply, automotive qualification, and dual-polarity isolated bias rails.

Supply support for STEVAL-A6986IV1 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, sensors, and analog devices for automotive, industrial, and consumer markets.

The STEVAL-A6986IV1 belongs to ST's automotive power evaluation platform family, developed specifically to accelerate design-in of isolated DC-DC solutions for high-reliability EV power electronics subsystems.

FAQ

What is the purpose of the TL431 on the STEVAL-A6986IV1 board?

The TL431 serves as a precision shunt voltage reference in the secondary-side regulation circuit. It works with a power transistor to stabilize the negative output voltage (−4.3 V) by adjusting conduction through feedback to the primary-side A6986I controller-enabling accurate, optocoupler-free isolation without compromising transient response.

Can the STEVAL-A6986IV1 generate only a single isolated output?

Yes. By removing D3 (the Zener diode generating the negative rail) and replacing C12 with a 0 Ω resistor, the board delivers only the positive isolated output (~+18 V). Fine-tuning R11 may be required to maintain regulation accuracy under varying load conditions.

How is the positive isolated output voltage adjusted on this board?

The positive output voltage is set via resistor divider R12 and R13 using the formula V_ISO = 2.49 × (R12 + R13)/R13. Changing either resistor alters the feedback ratio to the A6986I's FB pin, allowing precise calibration of the +18 V rail for different gate-driver requirements.

Does the board include EMI filtering, and can it be bypassed?

Yes-the board integrates an input EMI filter on the bottom side. If filtering is unnecessary or interferes with testing, a 0 Ω resistor can be placed on R16 (bottom-side footprint) to bypass the filter while maintaining signal integrity and layout symmetry.