Step-Up/Step-Down Converter Features Ultra-Low Quiescent Current

Abstract: This design is intended to be used in portable applications where the input power source is provided by three NiCd or NiMH cells (3.6V without load) and where the output voltage is 3V. When the input battery is fully charged, the input voltage is above 3V and when the power source is half or near fully discharged, the input voltage is below 3V.

A 3V, 100mA regulated output is generated with a typical quiescent current below 12µA. Input voltage ranges from 2V to 5V and power conversion efficiency is above 60%. It consists of a step-up converter (U1: MAX1833) followed by a LDO (U2: MAX8880). It offers a POK output signal that can be used as µP reset signal, and integrated reverse input battery protection.