38 V, 1.5 A synchronous step-down switching regulator evaluation board based on the L6981NDR for industrial power systems STMicroelectronics STEVAL-L6981NDR is based on the L6981NDR synchronous monolithic step-down regulator delivering up to 1.5 A DC.

Its wide input voltage range makes the solution suitable for a broad range of applications.

The device implements peak current mode architecture in a SO 8L package with internal compensation to minimize design complexity and size.

The L6981 is available in low consumption mode (LCM) and low noise mode (LNM) versions. LCM maximizes efficiency at light-load with controlled output voltage ripple, making the device extremely suitable for battery-powered applications.

LNM makes the switching frequency constant and minimizes the output voltage ripple overload current range, meeting the specification for noise sensitive applications.

The EN pin manages the enable/disable function. The typical shutdown current is 2 μA when disabled. When the EN pin is pulled up, the device is enabled and the internal 1.3 ms soft-start takes place.

Pulse-by-pulse current sensing on both power elements implements effective constant current protection while thermal shutdown prevents thermal run-away.

• 3.5 V to 38 V operating input voltage


• Output voltage from 0.85 V to VIN


• 3.3 V and 5 V fixed output voltage versions


• 1.5 A DC output current


• 17 μA operating quiescent current (fixed Vout part numbers)


• Internal compensation network


• Low noise mode version for noise sensitive applications


• 2 μA shutdown current


• Internal soft-start


• Enable function


• Overvoltage protection


• Output voltage sequencing


• Thermal protection


• SO-8 package


• Synchronization with external clock for LNM devices