Use the LDO LD39020DTPU31R linear regulator from STMicroelectronics to maintain a constant output voltage. It has an overall accuracy of ±2 %. Its typical dropout voltage at current is 0.035@30mA|0.2@200mA V. This voltage regulation device's single output can produce a current up to 0.2 A. With a small input voltage of 1.5 V and a max of 5.5 V, this will supply sufficient power to your circuit. With a fixed output that has a voltage of 3.1 V, this is power management at its best. By operating at a load regulation of 10mV(Typ) and line regulation of 0.02%/V(Typ) you can provide a constant voltage at your output. This product will be shipped in tape and reel packaging so that components can be mounted effectively. This voltage regulation device has a minimum operating temperature of -40 °C and a maximum of 125 °C. Its polarity is positive. The maximum dropout voltage is 0.35@200mA V.