TPS51218 Step-Down Controllers Texas Instruments TPS51218 Step-Down Controllers for notebook power supply is a small, single buck controller with adaptive on-time D-CAP™ mode. The TI TPS51218 features a small package with minimal pin-count that saves space on the PCB. A dedicated EN pin and pre-set frequency selections simplify the design. The TPS51218 step-down controller features a wide input voltage range of 3V to 28V and an output voltage range of 0.7V to 2.6V.