The 3.3 V regulator sourced by Vregin on the F34A is used to output a 3.3 V signal on the VDD pin that can be used to power external devices. The T62x and T32x families have a 3.45 V regulator instead of a 3.3 V regulator sourced by Vregin. There are no firmware requirements when looking into the different supply rails. Any design considerations regarding the power pertains to the external connections.

