DEVKIT-MPC5744P 12V supply with CAN

[philma]

Hi all,

I have a question regarding the 12V power supply of the DEVKIT-MPC5744P.

The Quick Start Guide says that this external supply is necessary for CAN communication (p.14). Hower I was able to implement a simple CAN communication through CAN_0 with just the USB supply.

So in which cases do I need the external supply?

Best regards,

Philipp

[PetrS]

Hi,

It depends how the jumper on J13 is placed.

For 1-2 connection external 12V is needed, for 2-3 the USB cable is enough.

BR, Petr

[philma]

Hi,

thanks for the respond.

The jumper setting is clear to me. But the question is, do I need 12V supply for CAN/LIN?

On p.9 of the QSG it is written

" For high power/current consuming applications (like using external shield boards) use “External 12 V Supply” only"
This makes sense as an USB port has limited power.

But on p.14 it also says:

"12V must be used for CAN and LIN/UART communication."

Why should it be a "must" as it is not that power consuming? As mentioned I was able to power CAN with just USB supply anyway.

Best regards,

Philipp

[PetrS · Accepted solution]

Hi,

Most probably the recommendation is to ensure reliable operation under all condition.

The CAN transceiver can consume about 100mA in the present of Bus failure. Its VDD is connected to 5V0_SR, for the USB supply only the overall current sourced from the 5V0_SR can be over the current the USB can deliver.

So the CAN communication on USB supply can work in normal condition, you have, but could not be enough for extremes.

Thus 12V power options is recommended.

BR, Petr