LM3687

LM3687 Step-Down DC-DC Converter with Integrated Low Dropout Regulator and Startup Mode December 4, 2007 LM3687 Step-Down DC-DC Converter with Integrated Low Dropout Regulator and Startup Mode General Description The LM3687 is a step-down DC-DC converter with an integrated low dropout Linear Regulator optimized for powering ultra-low voltage circuits from a single Li-Ion cell or 3 cell NiMH/NiCd batteries. It provides a dual output with fixed output voltages and combined load current up to 750mA in post www.DataSheet4U.com regulation mode or 1100mA in independent mode of operation, over an input voltage range from 2.7V to 5.5V. There are several different fixed output voltage combinations available (refer to table 'Voltage Options'). The Linear Regulator being driven from the fixed output voltage of the buck converter (post regulation) translates to high efficiency. 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 efficiency over the full load current range. During full-power operation, a fixed-frequency 1.8MHz (typ.) PWM mode drives loads from ~80mA to 750mA max. Hysteretic PFM mode extends the battery life through reduction of the quiescent current during light loads and system standby. The LM3687 also features internal protection against overtemperature, current overload and under-volt...