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TCAN1051H-Q1: Maximum Drive current of the RxD pin

Part Number: TCAN1051H-Q1
Other Parts Discussed in Thread: ISO1042


We are using the TCAN1051HDQ1 in an isolated CAN circuit. The isolation is performed with a pair of opto-couplers which isolate the RxD and TxD signals. The RxD signal of the transceiver turns the LED of the optocoupler On by sinking 7mA. This is within the absolute maximum rating of the pin (at 8mA) but we are unsure if this is within your recommended range as defined in section 6.4 of your datasheet. It is not clear to us what is defined as positive/negative current in relation to the pin. Please can you confirm whether 7mA is acceptable and if not is there any way to get around this problem i.e. an alternate part from TI? We are fairly limited on how much we can change the circuit as this is an upgrade to an existing product but we are open to any suggestions you may have.

Best Regards,


  • Hi James,

    This solution should be fine in terms of not damaging the transceiver because the absolute maximum is not violated. The recommended output of 2mA describes the output current where the specified output voltage can be maintained. With a 7mA load on the RXD pin, it's likely that the Voh/Vol levels from the datasheet will not be met. However, because the current can still be provided, this should be fine for turning on the LED (depending on the opto of course). 

    For a different solution, you might consider ISO1042. This is a TCAN1042 CAN transceiver and digital isolator integrated into the same package. For this device, the RXD and TXD signals are isolated across the package from the CAN pins. The digital isolator also offers several advantages to an optocoupler. Let me know if you're interested in this solution if there is room for modification with this design. 

    Eric Schott

  • Thanks Eric, that's answered my question