External power supply is needed when power requirements exceed USB limits

The F2800137 evaluation kit ships with a USB cable and is designed to be powered by way of USB. However, in extreme cases the board/controlCARD can require more power than the 5 V @ 500 mA (USB 3.0 - 900 mA) that a computer USB port can provide. This is especially true when additional circuitry has been added to the TMDSHSECDOCK. In such cases, it is recommended to use an external 5 V power supply (2.5 mm inner diameter x 5.5 mm outer diameter) and plug the power supply into J1 on the TMDSHSECDOCK. A compatible supply such as:

• CUI SMM6-5-K-P6 + SMI-US-5

5-V power supply instability can lead to device resets

The 5-V rail on the TMDSCNCD280039C controlCARD can be powered from an on-board USB connector or from a baseboard like the TMDSHSECDOCK. A switch device on the controlCARD automatically selects the 5-V input power source for the controlCARD without the need for user configuration.

A loss of power or glitching on the baseboard 5-V power source can cause the automatic switch to disconnect from both power sources for several milliseconds. This momentary loss of power can cause a brownout condition on the MCU, triggering a device reset. To avoid this condition, make sure that the baseboard power supply remains at 0 V or 5 V during code execution.