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SN65HVD257: Current consumption for SN65HVD257DR

Part Number: SN65HVD257

Hi,

I am going to use SN65HVD257DR for one of the application.

I am bit concerned about the ICC which is 130-180mA in Driving dominant-Bus fault condition.

ambient temperature is 50degree.

I am calculating stress analysis at this current it is crossing 125degrees which is equal to Operating temperature.

Could you please help me with the Same ic and What is bus fault condition>

and it is really useful in my design?

  • Hi Deepak,

    This is for the case where the device is driving dominant but the CANH pin is shorted to -12 V.  In determining how relevant a case this maybe to your thermal calculations, you may want to keep in mind:

     - Is it possible for the CANH pin to see -12 V?  In an automotive environment, this may result from an incorrect battery connection.  If that were to occur, though, is it also possible that the transceiver and controller/MCU would be properly powered in order to operate in normal mode and drive dominant-state outputs?

     - When the transceiver drives a dominant but CANH is shorted to a low voltage, the resulting differential voltage is very low.  This means that the transceiver will still report a recessive bus state back to that node's controller.  The mismatch in TXD and RXD states will be seen as an error by the controller on that node, and it will send an error frame.  However, since the issue persists errors will continue to accumulate.  The controller will quickly transition to the error passive or bus off state and cease driving TXD high, thus limiting the duration that this high-current condition can occur.

     - The SN65HVD257 device enters thermal shutdown to protect itself when the internal temperature reaches ~170 C.  In this state, the output driver is disabled and the internal power dissipation is minimal.

    Regards,
    Max

  • What is the VBUS?

    CAN Bus I/O voltage (CANH, CANL) shows that -27V to 40V

  • Yes, -27 V to +40 V is the absolute maximum supported range.

    Regards,
    Max

  • When such conditions comes into picture?

    As CANH and CANL are driving through the IC Voltage?

    So what is the chance of -27V to 40V

    If we connect -27V to the CANH pin->it is equivalent to applying -12V which leads to Draw max current stated in datasheet

  • These voltages would only occur if they were applied from some external source; the IC itself could not generate them.  Some common examples would be a short-circuit to a power supply or battery line or from transient stresses that may couple (such as load dump surges on battery lines).  So, the chances of seeing them in most cases are very small but it would depend on how your end system will be operated.  Yes, shorting CANH to -27 V would behave similarly to shorting to -12 V; the maximum short-circuit output current will flow from the high-side CANH driver.

    Regards,
    Max