The MAX1809 uses a unique current-mode, constantoff-time, PWM control scheme that allows the output to source or sink current. This feature allows energy to return to the input power supply that otherwise would be wasted. The programmable constant-off-time architecture sets switching frequencies up to 1MHz, allowing the user to optimize performance trade-offs between efficiency, output switching noise, component size, and cost. The MAX1809 features an adjustable soft-start to limit surge currents during startup, a 100% duty-cycle mode for low-dropout operation, and a low-power shutdown mode that disables the power switches and reduces supply current below 1A. The MAX1809 is available in a 28-pin QFN with an exposed backside pad, a 28-pin thin QFN, or a 16-pin QSOP.