Apply 3.3 V to the J23 header. The acceptable supply voltage range at the board is 3.1 V to 3.5 V, and the device can draw up to 1.3 A during operation, so resistive drop in supply cables can be non-negligible. The on-board LDO has an about 40mA ground current for converting 3.3V to 2.5V supply. Furthermore, enabling or disabling various system functions can change the device current by 50% or more.