Surface Mount Step-Down Converter, switching regulator circuit, on off switch

 MP2456 Series 50 V 0.5 A 1.45 MHz Surface Mount Step-Down Converter - TSOT23-6

https://www.futureelectronics.com/p/semiconductors--analog--regulators-reference--switching-regulators/mp2456gj-z-monolithic-power-systems-8166082