CAN-FD clocked by FIRC

[Catosh]

Hi all, 

According to this document (Robustness of a CAN FD Bus System) with a clock of 40MHz the oscillator tolerance range accepted in CAN FD for bitrates from 500Kb/s up to 10Mb/s is in the range 0/0.75%.

Furthermore, to achieve standard baud rates normally an external oscillator of 40MHz is required. 

My question is: 

The CAN peripheral on the S32K1xx MCUs is meant to be used in conjunction with an external oscillator or with an internal oscillator?
FIRC oscillator has a worst case tolerance in the range of the 1% (up to 1.1 above 125degrees).

In K116 the FIRC is the main clock source, the implication here is that is not possible to use the MCU and CAN peripheral for high baud rates without external oscillator - or am I wrong?

Is there some reference or application note from NXP that relates CAN baud rates and oscillator/internal clock requirements?

Any hint in general?

Kind Regards, 

L.

P.S.

Please note that uisng two EVB we were able to run correctly CAN-FD examples. Then the validation with other commercial tools has some troubles, hence my question about FIRC and ext osc. 

[danielmartynek · Accepted solution]

Hi,

You can refer to AN1798 CAN Bit Timing Requirements.

It depends on the system and configuration.

If higher tolerace is required than the FIRC specification, you should use SOSC.

Regards,

Daniel

[ben_chin]

Hello，

If the oscillator is used as the clock source, what frequency of oscillator is required for the baud rate of CAN FD 500Kbps/2Mbps, and is frequency 8Mhz of oscillator OK?