TCAN4550-Q1: some spec questions

Eric Schott1 said:

I'm not sure what thresholds you're asking about. The digital input threshold voltages are 0.3 * Vio and 0.7 * Vio for all digital pins (SPI, nRST). The CAN receiver, WAKE input, and oscillator input thresholds are also included in the datasheet. Which specifications are you looking for?

this is what I talked about VIT. this screenshot above is from TCAN1044 datasheet.

Eric Schott1 said:

why here is a difference  for Vdom and Vrec range between 4450 and 1044?

Can you point out the exact specifications you are referring to here? Almost every specification here is shared between devices as this behavior is defined by the ISO 11898-2 CAN specification. 
Note that some of the upper ranges or references may be different because TCAN4550 generates its own Vcc reference with its internal LDO from Vsup. TCAN1044 specified this behavior across a range of externally supplied Vcc. 

Here is screenshot from TCAN1044 and TCAN4550:

TCAN1044:

TCAN4550:

you can see here is slight difference. does it come from different supply for VCC?

Eric Schott1 said:

TCAN4550 supports the physical layer requirements of SAE J2284-2. The other sections of this standard build on the ISO 11898 physical and protocol layers for system-level considerations. TCAN4550 is able so support the transceiver-level requirements for the physical layers of these standards, and the CAN protocol used by TCAN4550 can support higher-level software that implements the system-level requirements of these standards. 

double confirm, for " does 4450 support SAE J2284-1,  SAE J2284-4,  SAR J2284-5 from physical layer?" can we say the answer is "yes and TCAN4550 can support all physical layer standards built on ISO11898"?

thank you!

B&R

Yuan

Hi Yuan,

Receiver input thresholds:

The ISO 11898-2 CAN specification defines the input threshold range for CAN transceivers to be what is shown on the TCAN4550 datasheet. The TCAN1044 shows a slightly larger overall range to to the differential receiver, but it all overlaps with the ISO defined range. I expect this difference mainly came from the way the devices were characterised, as there is no defined behavior for CAN receivers when the differential is outside of the ISO range (-3V to +8V). Therefore, I don't expect much difference in behavior between these devices at these larger ranges, but we technically do not specify TCAN4550's receiver behavior outside of the ISO range. 

SAE J2284 compliance:

Yes, TCAN4550 can support all physical layers that require ISO 11898-2. However, some standards that build off of this spec will add additional requirements. To my knowledge, the SAE standards only require the physical layer defined by the ISO standard, so I am confident saying we support this. Keep in mind this may not be the case for all ISO 11898-2 derived standards.

For the protocol layer, I wanted to be sure we mentioned that there will need to be some upper-level firmware to deal with the more system-level requirements of the SAE functional definitions. Because TCAN4550 only deals with the basics of the ISO 11898-1 protocol layer, it is capable of supporting a variety of higher level implementations. It is good to let customers know that such higher level functions will still need to be considered in the processors firmware.

Regards,
Eric Schott