Integrated regulators simplify efficient power conversion

8th April 2021
Alex Lynn

STMicroelectronics has introduced L6981 synchronous step-down regulators, extending the family of high-efficiency converters that simplify power-supply design by integrating power elements, feedback circuitry, and safety features on-chip.

Rated to deliver up to 1.5A, with 90% typical efficiency at full load, the L6981 converters are available in two variants optimised for light-load efficiency and noise performance.

The L6981C for low-current operation uses pulse skipping to maximise efficiency at light loads extending the runtime of battery-powered devices. The L6981N prioritises low noise by operating permanently in PWM (pulse-width modulation) mode at constant switching frequency and minimising voltage ripple at light loads.

Both variants can accept an input voltage from 3.5 to 38V, making them well suited to use in 24V industrial bus-powered applications, 12 and 24V battery-powered equipment, HVAC power supplies, decentralised intelligent nodes, smart sensors, and always-on applications. The output voltage can be adjusted from 0.85V up to the input-voltage value using external resistors.

Integrated features include high-side and low-side NMOS power transistors, feedback-loop compensation, over-voltage protection, and thermal protection. There is also soft-start circuitry that limits inrush current and ensures a constant output-voltage slope. An Enable pin is provided, which permits power-up/power-down sequencing and allows a synchronising clock signal to be applied to the L6981N low-noise converters. The L6981 is included in ST’s 10-year longevity program that ensures long-term component supply.

The STEVAL-L6981CDR evaluation board for the low-current converter and STEVAL-L6981NDR for the low-noise version are available to help designers accelerate device selection in power-supply development.

The L6981 is in production now, in the proven, rugged SO8L package, from $1.00 for orders over 1,000 pieces.

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