The LM3671 step-down DC-DC converter is optimized for powering low voltage circuits from a single Li-Ion cell battery and input voltage rails from 2.7 V to 5.5 V. It provides up to 600-mA load current, over the entire input voltage range. There are several different fixed voltage output options available as well as an adjustable output voltage version range from 1.1 V to 3.3 V. The device offers superior features and performance for mobile phones and similar portable systems. Automatic intelligent switching between PWM low-noise and PFM low-current mode offers improved system control. During PWM mode, the device operates at a fixed-frequency of 2 MHz (typical). Hysteretic PFM mode extends the battery life by reducing the quiescent current to 16 µA (typical) during light load and standby operation. Internal synchronous rectification provides high efficiency during PWM mode operation. In shutdown mode, the device turns off and reduces battery consumption to 0.01 µA (typical). A high-switching frequency of 2 MHz (typical) allows use of tiny surface-mount components. Only three external surface-mount components, an inductor, and two ceramic capacitors, are required. For all available packages, see the orderable addendum at the end of the datasheet.