The TMI3451 is a synchronous buck controller mainly for widely varying input step-down regulator applications. The control method is based upon current mode control that enables maximum performance under transient conditions. The output voltage can be programmed by the FB pin. It operates as a Buck mode while the input voltage is sufficiently greater than the regulated output voltage and transitions to the low dropout operation mode with maximum duty cycle at 99.5% as the input voltage very approaches the output voltage. It also features an adjustable soft-start function and cable impedance compensation function and offers protection features including input UVLO, cycle-by-cycle current limit, over power protection (OPP), output short protection (SCP) or OVP and thermal shutdown. In addition, it features selectable Forced Continuous Conduction Mode (FCCM) or Discontinuous Conduction Mode (DCM) operation for light load. The TMI3451 is available in compact QFN3x3-20.