The ADP1872/ADP1873 are versatile current-mode， synchronous step-down controllers that provide superior transient response， optimal stability， and current limit protection by using a constant on-time， pseudo-fixed frequency with a programmable currentsense gain， current-control scheme. In addition， these devices offer optimum performance at low duty cycles by using valley currentmode control architecture. This allows the ADP1872/ADP1873 to drive all N-channel power stages to regulate output voltages as low as 0.6 V. The ADP1873 is the power saving mode （PSM） version of the device and is capable of pulse skipping to maintain output regulation while achieving improved system efficiency at light loads （see the Power Saving Mode （PSM） Version （ADP1873） section for more information）。 Available in three frequency options （300 kHz， 600 kHz， and 1.0 MHz， plus the PSM option）， the ADP1872/ADP1873 are well suited for a wide range of applications. These ICs not only operate from a 2.75 V to 5.5 V bias supply， but can also accept a power input as high as 20 V. In addition， an internally fixed， soft start period is included to limit input in-rush current from the input supply during startup and to provide reverse current protection during soft start for a precharged output. The low-side current-sense， current-gain scheme and integration of a boost diode， along with the PSM/forced pulsewidth modulation （PWM） option， reduce the external part count and improve efficiency. The ADP1872/ADP1873 operate over the ?40°C to +125°C junction temperature range and are available in a 10-lead MSOP.