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TCAN334: TCAN334 abs spec

Hollis Liu
Intellectual 2535 points
Part Number: TCAN334

Hi team,

In TCAN334 datasheet, we can find the abs voltage for CANH/CANL is +-14V. The 14V here is that when VCC is powered, right? And if we connect the CANH/L to CAN bus, and don't power VCC, will the IC be damaged ? 

In my customer test, they have 2 TCAN334(A & B) on CAN BUS. And device B is powered up after device A. And we found, when device B is attached to the CAN BUS, the BUS voltage will be pulled low to be about 1V for about 500us, then recover. Does that make sense? 

  • +1
    TI__Mastermind 47895 points

    Hi Hollis,

    The absolute maximum specifications are for both a powered and unpowered device. The CAN bus can withstand ±14V (relative to GND pin) while Vcc is unpowered. 

    While the CAN transceiver is unpowered, it presents a load to the bus. This is because there is some leakage through the high impedance CAN pins in this state. When only one transceiver is active and weakly biasing the bus to a recessive level (1.85V), the load presented by the unpowered transceiver can cause the bus voltage to remain below the nominal recessive level. This is normal. Once both devices are active and biasing the bus, the nominal recessive voltage should be observed on CANH and CANL.

    Let me know if this correlates with what you are seeing and if you have any more questions.

    Regards,
    Eric Schott