Texas Instruments' LM2840, LM2841, and LM2842 are PWM DC/DC buck (step-down) regulators. With a wide input range from 4.5 V to 42 V, they are suitable for a wide range of applications such as power conditioning from unregulated sources. They feature a low R_DSON (0.9 Ω typical) internal switch for maximum efficiency (85% typical). Operating frequency is fixed at 550 kHz (X version) and 1.25 MHz (Y version), allowing the use of small external components while still being able to have low output voltage ripple. Soft-start can be implemented using the shutdown pin with an external RC circuit. This allows the user to tailor the soft-start time to a specific application.