The TPS51120 is a highly sophisticated dual current mode synchronous step-down controller. It is a full featured controller designed to run directly off a threeor four-cell Li-ion battery and provide high-power and 5-V and/or 3.3-V standby regulation for all the downstream circuitry in a notebook computer system. High current, 100-mA, 5-V or 3.3-V on-board linear regulators have glitch-free switch over function to SMPS and can be kept alive independently during standby state. The pseudo-constant frequency adaptive on-time control scheme supports full range of current mode operation including simplified loop compensation, ceramic output capacitors as well as seamless transition to reduced frequency operation at light-load condition. Optional D-CAPTM mode operation optimized for SP-CAP or POSCAP output capacitors allows further reduction of external compensation parts. Dynamic UVP supports VIN line sag without latch off by hitting 5V UVP. No negative voltage appears at output voltage node during UVLO, UVP, and OCP, OTP or loss of VIN.