I am working on a school project using the NRF51822 with SoftDevice 130 on a custom board and I aim to create an HID gamepad. I am working on my power supply circuit and my device will be powered by two AA batteries in series. When the batteries are new they have a voltage of +3.0V and for ease of design let's say that once they drop below +1.8V (the minimum for the internal LDO) that they are "dead".
Is it feasible to connect the batteries directly to the AVDD, VDD and GND pins and use the internal LDO? Would it be better to use an external regulator and if so, which do you recommend?