The NX2139A controller IC is a compact Buck controller IC with 16 lead MLPQ package designed for step down DC to DC converter in portable applications. It can be selected to operate in synchronous mode or non-synchronous mode to improve the efficiency at light load.Constant on time control provides fast response, good line regulation and nearly constant frequency under wide voltage input range. The NX2139A controller is optimized to convert single supply up to 24V bus voltage to as low as 0.75V output voltage. Over current protection and FB UVLO followed by latch feature. A built-in LDO controller can drive an external NMOSFET to provide a second output voltage from either PWM output source or other power source. Both PWM controller and LDO controller have separate EN feature. Other features includes: 5V gate drive capability, power good indicator, over voltage protection, internal Boost schottky diode and adaptive dead band control.