SPRUJ29A April 2022 – January 2023
External power supply is needed when power requirements exceed USB limits
The F2800157 evaluation kit ships with a USB cable and is designed to be powered using 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’s 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 power supply is:
5-V power supply instability can lead to device resets
The 5-V rail on the TMDSCNCD2800157 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.
CAN boot mode requires use of on-board crystal
The TMDSCNCD2800157 controlCARD supports the use of the CAN boot mode. This boot mode can be selected through switch S4. The CAN boot mode requires the use of an external crystal to clock the F2800157 device. Therefore, when using the CAN boot mode, the controlCARD must be configured to use the on-board crystal Y1 by setting switch S3 accordingly. See Section 6 for more information on the S3 and S4 switches.