TCAN4550: TCAN4550 – Specification Question

Hi Gary, 

These charts do not appear to be consistent with the TCAN4550 datasheet. Are you sure you are referencing the correct document? Please ensure you are using the latest version of the datasheet available on ti.com. 

The common-mode range for the CAN receiver in TCAN4550 is ±12V. This describes the allowable common-mode offset with respect to GND where the receiver will continue to operate normally. If the common-mode voltage exceeds this range, the receiver may not be able to properly monitor the bus. However, device damage will not occur until the voltage on the bus pins exceeds the absolute maximum ratings. 

The common-mode range is most often applicable for ground potential differences (GPD) in systems. Common-mode noise may also cause the voltage to exceed this limit, but this is more often a damage concern (abs max spec) due to the relatively infrequent presence of such transients. 

Regards,
Eric Schott

Gary,

V_BUS refers to the devices ability to withstand +/-58V relative to ground on CANH, CANL, or the differential voltage between the two. The common-mode range you show first is the voltage range that the device can correctly interpret CAN frames. The common-mode range of the TCAN4550 and TCAN4550-Q1 is +/-12V.

Were you wanting to know the device's ability to withstand damage, or interpret CAN messages correctly?

Regards,

Eric Hackett 

Thanks for your help.

As my understanding, I need CAN transceiver that can interpret CAN messages correctly with +/- 30V.

For spec review from my side, TCAN 1042 and ISO 1042 can meet but TCAN4550 not.

If that is correct, please recommend another one to replace TCAN4550.

BR, Gary

Hi Gary, 

This is correct. Devices such as TCAN1042 and TCAN1043 support an extended common mode range of ±30V. We do not have a TCAN4550 equivalent that supports this range. 

If a two-chip solution is possible, TCAN4550 can be used in controller only mode and an extern transceiver such as TCAN1042 or TCAN1043 may be used to interface directly with the bus. Does this sound like a valid solution here?

Regards,
Eric Schott

Hi Schott,

Thanks for your support.

Because our MCU don’t support CAN-FD controller. We only have SPI interface. And we need the Isolation. So we choose ISO1042.

This is two-chip solution, ISO1042 + TCAN4550-Q1. My question is how to connect the TX/RX(ISO1042) to the CANH/CANL(TCAN4550)? Please see the Gree block below. Do you have reference design or schematic to share? Or you have another solution to suggest? Thanks

BR, Gary

Hi Gary,

The digital outputs of the CAN controller can be routed to the GPIO pins of TCAN4550 for use with an external transceiver. Test mode can be enabled and configured in the mode control register (h0820 [21] and [0]). The connections to an external transceiver will use GPIO1 as RXD and GPO2 as TXD. See the below graphic. 

Let me know if this is clear. 

Regards,
Eric Schott