MAX756

The MAX756/MAX757 are CMOS step-up DC-DC switch- ing regulators for small, low input voltage or battery-pow- ered systems.  The MAX756 accepts a positive input voltage down to 0.7V and converts it to a higher pin- selectable output voltage of 3.3V or 5V.  The MAX757 is an adjustable version that accepts an input voltage down to 0.7V and generates a higher adjustable output voltage in the range from 2.7V to 5.5V.  Typical full-load efficiencies for the MAX756/MAX757 are greater than 87%.

The MAX756/MAX757 provide three improvements over previous devices.  Physical size is reduced-the high switching frequencies (up to 0.5MHz) made possible by MOSFET power transistors allow for tiny (<5mm diameter) surface-mount magnetics.  Efficiency is improved to 87% (10% better than with low-voltage regulators fabricated in bipolar technology).  Supply current is reduced to 60A by CMOS construction and a unique constant-off-time pulse-frequency modulation control scheme.