The output voltages are programmable from 1.2V to VIN using external feedback resistors, or can be preset to 1.8V or 3.3V for output 1 and 1.5V or 2.5V for output 2. When one output is higher than 1.2V, the second can be configured down to sub-1V levels. Output accuracy is better than 1% over variations in load, line, and temperature. Internal soft-start reduces inrush current during startup. All devices feature power-on reset ( POR ). The MAX1971 includes a reset input (RSI), which forces POR low for 175ms after RSI goes low. The MAX1970 and MAX1972 include an open-drain power-fail output (PFO) that monitors input voltage and goes high when the input falls below 3.94V. For USB-powered xDSL modems, this output can be used to detect USB power failure. A minimum switching frequency of 1.2MHz ensures operation outside the xDSL band.