Integrated 1.5A synchronous regulators simplify high-efficiency power conversion

As a boost to its family of high-efficiency converters, STMicroelectronics has introduced the L6981 synchronous step-down regulators. These new additions help simplify power-supply designs by integrating power elements, feedback circuitry and safety features on-chip.

Rated to deliver up to 1.5A, with 90 per cent 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 pulse-width modulation (PWM) mode at constant switching frequency and minimising voltage ripple at light loads.

Both variants can accept an input voltage from 3.5V to 38V, making them well-suited for use in 24V industrial bus-powered applications, 12V 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.

ST states that the L6981 is included in its 10-year longevity programme 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 a rugged SO8L package and priced from $1.00 for orders of more than 1,000 pieces.

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