L6981 Synchronous Step-down Converters with Low Quiescent Current for Simplifying High-Efficiency Power Conversion

STMicroelectronics has introduced the L6981 synchronous step-down regulators rated to deliver up to 1.5A with 90% typical efficiency at full load. With the new device, the company has extended its family of high-efficiency converters that simplify the power-supply design by integrating power elements, feedback circuitry, and safety features on-chip.

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

Accepting input voltage from  3.5V to 38V the new devices are suitable for 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.

Along with a soft start circuit that limits inrush current and ensures a constant output-voltage slope, the devices also feature high-side and low-side NMOS power transistors, feedback-loop compensation, over-voltage protection, and thermal protection. The devices include an Enable pin that permits power-up/power-down sequencing and allows a synchronizing clock signal to be applied to the L6981N low-noise converters.

The L6981 synchronous step-down regulators are available in a rugged SO8L package from $1.00 for orders over 1000 pieces. Designers accelerate device selection in power-supply development by leveraging the STEVAL-L6981CDR evaluation board for the low-current converter and STEVAL-L6981NDR for the low-noise version.

Features of L6981 Synchronous Step-down Regulators

• 3.5 V to 38 V operating input voltage
• The 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
• Overvoltage protection and Thermal protection
• Output voltage sequencing
• Synchronization to an external clock for LNM devices

Note: More technical information can be found in the L6981 Datasheet linked at the bottom of this page and on the product page of L6981 Synchronous Step-down Regulators.