The LM3671 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 600mA load current, over an input voltage range from 2.8V to 5.5V. There are several different fixed voltage output options available as well as an adjustable output voltage version. The device offers superior features and performance for mobile phones and similar portable applications with complex power management systems. Automatic intelligent switching between PWM low-noise and PFM low-current mode offers improved system control. During full-power operation, a fixed-frequency 2 MHz (typ). PWM mode drives loads from 70 mA to 600 mA max. Hysteretic PFM mode extends the battery life through reduction of the quiescent current to 16 A (typ) at light loads and system standby. Internal synchronous rectification provides high efficiency. In shutdown mode (Enable pin pulled low) the device turns off and reduces battery consumption to 0.01 A (typ). The LM3671 is available in a SOT23-5 package with Pb and No Pb (Lead free) versions. A high switching frequency - 2 MHz (typ) - allows use of tiny surface-mount components. Only three external surface-mount components, an inductor and two ceramic capacitors, are required.