LM3671,pdf datasheet (2MHz , 6

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 μA (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 μA (typ).