The AC-MB motherboard is powered from a single 5V power supply. However, the motherboard has different low-dropout regulators (LDOs) integrated that provide the required power supplies to the different blocks of the board. The block diagram depicting the power structure of the AC-MB is shown in Figure 3-5. The AC-MB can be powered from the host computer by using the USB 5V power supply (VBUS) by shorting header J5, USB POWER. Additionally, the AC-MB can be powered from an external power supply connected to terminal J4, EXTERNAL POWER. Header J5 must be open for external supply operation. The IOVDD voltage for the digital signals that is provided to the evaluation module is generated on the motherboard from the main power supply (USB or external). The voltage levels available are 1.2V, 1.8V and 3.3V, and can be selected via the J3 header IOVDD. Default setting for TAS2020EVM operation is 3.3V; 1.2V operation cannot be used for TAS2020EVM. When the motherboard is fully powered and the power supplies from the onboard LDOs are correct, the green POWER LED (D3) turns ON. The USB READY LED indicates that a successful USB communication is established between the AC-MB and the host computer.

Figure 3-6 Power -Supply Distribution of the AC-MB