The TPS51427A is a dual synchronous step-down controller designed for notebook and mobile communications applications. This device is part of a low-cost suite of notebook power bus regulators that enables system designs with low external component counts. The TPS51427A includes two pulse-width-modulation (PWM) controllers, SMPS1 and SMPS2. The output of SMPS1 can be adjusted from 0.7 V to 5.9 V, while the output of SMPS2 can be adjusted from 0.5 V to 2.5 V. This device also features a low-dropout (LDO) regulator that provides a 5-V/3.3-V output, or adjustable from 0.7-V to 4.5-V output via LDOREFIN. The fixed-frequency emulated adaptive on-time control supports seamless operation between PWM mode under heavy load conditions and reduced frequency operation at light loads for high-efficiency down to the milliampere range.