The LM3691 step-down DC-DC converter is optimized for powering ultra-low-voltage circuits from a single Li-Ion cell or 3 cell NiMH/NiCd batteries. It provides up to 1-A load current over an input voltage range from 2.3 V to 5.5 V. There are several different fixed voltage output options available. The LM3691 has a mode-control pin that allows the user to select Forced PWM mode or ECO mode that changes modes between gated PWM mode and PWM automatically, depending on the load. In ECO mode, the device offers superior efficiency and very low IQ under light load conditions. ECO mode extends the battery life through reduction of the quiescent current during light load conditions and system standby. The LM3691 is available in a 6-pin DSBGA package. Only three external surface-mount components, a 1-μH inductor, a 4.7-μF input capacitor, and a 4.7-μF output capacitor, are required. For all available packages, see the orderable addendum at the end of the data sheet.