LM3670

LM3670 Miniature Step-Down DC-DC Converter for Ultra Low Voltage Circuits December 2004 LM3670 Miniature Step-Down DC-DC Converter for Ultra Low Voltage Circuits General Description The LM3670 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 350 mA load current, over an input voltage range from 2.5V 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 1 MHz (typ). PWM mode drives loads from ∼70 mA to 350 mA max, with up to 95% efficiency. Hysteretic PFM mode extends the battery life through reduction of the quiescent current to 15 µA (typ) during light current loads and system standby. Internal synchronous rectification provides high efficiency (90 to 95% typ. at loads between 1 mA and 100 mA). In shutdown mode (Enable pin pulled low) the device turns off and reduces battery consumption to 0.1 µA (typ.). The LM3670 is available in a SOT23-5 package. A high switching frequency - 1 MHz (typ) - allows use of tiny surface-mount components. Only three external surfacemount components, an inductor and two ceram...