STMicroelectronics A6986I and L6986I DC/DC converter ICs

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Optimised for isolated buck regulator designs, the STMicroelectronics A6986I and L6986I DC/DC converter ICs have a wide input-voltage range and low quiescent current for robust and energy-efficient operation in automotive and industrial applications up to 5 W.

The isolated buck topology should lower the bill of materials in systems that require a regulated non-isolated primary voltage and one or more isolated secondary voltages. The secondary voltage is governed by the transformer turns ratio and no optocoupler is needed for regulation. Common uses include powering gate drivers for SiC MOSFETs and IGBTs that require asymmetrical isolated power rails and powering isolated interfaces such as RS-232, I²C and SPI.

Typical applications for the AEC-Q100 Grade-1 qualified A6986I converters include automotive onboard chargers (OBC) and hybrid/electric-vehicle (H/EV) traction drives. The 100% duty-cycle capability and wide input-voltage range, from 4 to 38 V, meet the cold-crank and load-dump specifications for automotive systems. The industrial-grade L6986I is suitable for motor drives, solar power-conditioning systems, uninterruptible power supplies (UPS) and welders.

The converters operate in forced-PWM mode with peak-current-mode control to regulate the primary output voltage. An extended negative current limit on the primary side gives extra flexibility for a suitable secondary current using a typical transformer coil ratio. The devices feature programmable soft-start to enable pulse-by-pulse current sensing for constant-current protection in the primary side. A preset current-sense blanking time of 300 ns filters oscillations generated by the transformer leakage inductance and enables stability during high-side switching transitions. Overvoltage and thermal shutdown protection are built in and there are external pins for synchronisation and setting the switching frequency.

For more information: www.st.com/iso-buck-converters.