The TPS61291 is a boost converter with pin selectable output voltages and an integrated bypass mode. In bypass operation, the device provides a direct path from the input to the system and allows a low power micro controller (MCU) such as the MSP430 to operate directly from a single 3V Li-MnO2 battery or dual alkaline battery cells. In bypass mode the integrated feedback divider network for boost mode operation is disconnected from the output and the quiescent current consumption drops down to only 15nA (typical). In boost mode the device provides a minimum output current of 200mA at 3.3V VOUT from 1.8V VIN. The boost mode is used for system components which require a regulated supply voltage and cannot directly operate from the input source. The boost converter is based on a current-mode controller using synchronous rectification to obtain maximum efficiency and consumes typically 5.7µA from the output. During startup of the boost converter, the VSEL pin is read out and the integrated feedback network sets the output voltage to 2.5V, 3V or 3.3V. Bypass mode or boost mode operation is controlled by the system via the EN/BYP pin. The device integrates an enhanced bypass mode control to prevent charge, stored in the output capacitor during boost mode operation, from flowing back to the input and charging the battery. The device is packaged in a small 6-pin SON package (DRV) measuring 2.0mm × 2.0mm × 0.75mm.