Kinetis MicrocontrollersのトピックRe: Internal oscillator good enough for CAN bus?

Internal oscillator good enough for CAN bus?

claybarclay — Tue, 17 Jan 2017 15:29:09 GMT

Is the internal 4 Mhz oscillator in a kinetis-k-series‌ K10 accurate enough for high speed #can 2.0 #bit timing or must we have an external crystal on our board?

Re: Internal oscillator good enough for CAN bus?

claybarclay — Tue, 17 Jan 2017 15:31:20 GMT

I know the internal oscillators were not good enough for USB until they got the 48 MHz included but I am not sure about CAN on the older 4 MHz parts.

Re: Internal oscillator good enough for CAN bus?

egoodii — Tue, 17 Jan 2017 19:48:09 GMT

Tolerance is, of course, related to your bitrate and other tolerance factors, but suffice it to say that ANY CAN interface is going to need better than 1% tolerance, and even that cannot be held by internal chip oscillators. In general, you can say that the semi-synchronous nature of CAN requires frequency error on the order of <0.1% to keep all participants in lock-step, so definitely crystal-based.