12ZVMC CAN external regulator problem...

[draganandric]

Hi,

I have problem with S912ZVMC12F3MKH device. It is BLDC controller with CAN communication and  PNP transistor which supplies power to external CAN transceiver. Everything works fine (CAN communication is functional...) for a while, about 3-4 power cycles but then 12ZVMC fails (MCU draws 140mA), sometimes together with PNP transistor or CAN transceiver.

 Checking the circuit found that BCTLC pin is connected properly, although the base resistor was 5k6 and capacitors had lower value. I did not tried to change it yet.

The data sheet says that BCLTC pin should enabled  after startup. I am not sure if that was implemented in software.

Is there an example that I can suggest to our software person ?

Ihat else could be reason that external CAN power supply fails after working for a while, at a bench no harsh conditions? I will change base resistor to 1k. Please suggest additional steps.

Thank you,

Dragan  

[lama]

Hi,

Please check in your design: Recommendation for S12ZVM128 derivatives “On the ZVMC128 a diode is recommended between VDDA and VDDC, whereby the anode is connected to VDDC.”

( If we do not have the diodes and board is started up very quickly from a non 0V VDDC (so brown out situation with fast rise time) VDDC can overshoot extremely. On zvmc256 and S12ZVC the diode is internal already present.)

At the beginning of the code, for example as a first code in the main function you should mirror your external HW configuration in the internal MCU setup – register CPMUVREGCTL - check it bit by bit.

It is not suitable to have enabled both EXTXON and INTXON. If you use/do not use BJT connected to VDDX (see power domain overview and corresponding chapters in the data sheet (I suggest to download the last one) - good to use search keyword “bctl”) then EXTCON,INTCON should be set to 0B10/0b01.

Best regards,

Ladislav