Maxim offers an amazing portfolio of wide input voltage range power controllers and converters (the latter have integrated FETs). Care must be taken when designing with these devices if operating over a wide input voltage range is desired. All step down power controllers have a minimum on-time. Depending on the operating frequency and output voltage chosen, this minimum on-time will limit the maximum input voltage for operation. The controller devices will have overheads and maximum on-time that can limit the minimum input voltage for operation as well. The solution is to use the Maxim simulation environment, EE-Sim, to simulate all extremes of the application over input voltage, output voltage and output current. The knobs available to optimize the design would be switching frequency, inductor value and of course, input voltage range.