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New High-Efficiency 1.5A Synchronous Regulators from ST


The L6981 is rated to deliver up to 1.5A, with 90% typical efficiency at full load


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

These regulators are rated to deliver up to 1.5A, with 90% typical efficiency at full load. The L6981 converters are available in two variants optimized for light-load efficiency and noise performance.

Click for Larger Image - New High-Efficiency 1.5A Synchronous Regulators from ST The L6981C for low-current operation uses pulse skipping to maximize efficiency at light loads extending the runtime of battery-powered devices. The L6981N prioritizes low noise by operating permanently in PWM (pulse-width modulation) mode at constant switching frequency and minimizing voltage ripple at light loads.

Both variants can accept an input voltage from 3.5V to 38V, making them well suited to use in 24V industrial bus-powered applications, 12V and 24V battery-powered equipment, HVAC power supplies, decentralized 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 synchronizing clock signal to be applied to the L6981N low-noise converters.

Features of the L6981 Synchronous step-down Converter include:

  • 3.5 V to 38 V operating input voltage
  • Output voltage from 0.85 V to VIN
  • 1.5 A DC output current
  • Internal compensation network
  • Two different versions: LCM for high efficiency at light-loads and LNM for noise sensitive applications
  • 2 µA shutdown current
  • Internal Soft-start
  • Enable
  • Overvoltage protection
  • Output voltage sequencing
  • Thermal protection
  • Synchronization to external clock for LNM devices

More information on the L6981 1.5A synchronous step-down converter is available on the ST Web site at STMicroelectronics L6981 product page.


The company's Web site address is www.st.com.
[Reprinted with kind permission from STMicroelectronics - Release Date, 7th April, 2021]