The MCP16251 Single Cell Boost Converter With External UVLO Reference Design provides an example of how to optimize applications powered from a single AA cell battery by incorporating a ultra low power external under-voltage lockout circuit with hysteresis. The converter will not (re)start if the battery voltage is lower than 1.14V and will stop working if the battery voltage drops below 0.83V. The external ULVO circuit drains approximately 0.1-0.4 μA before start-up and 1 -2uA after start-up
Input voltage: one AA Primary or rechargeable battery Output voltage: 3.3V Output current: < 125 mA Typical Efficiency: Up to 96% Automatic PFM/PWM operation