• State Resolved
  • Locked Locked
  • Replies 4 replies
  • Subscribers 33 subscribers
  • Views 1346 views
  • Users 0 members are here
Support feedback
Options
Options
Related

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

SN65HVD252 Mis-wiring Protection

Loc Nguyen Huu
Prodigy 180 points
Other Parts Discussed in Thread: SN65HVD252

Hi,

We consider to use CAN transceiver SN65HVD252 for new DeviceNet products since it is introduced to meet and exceed for Devicenet requirement. I have a concern about Mis-Wiring Protection of this transceiver. Mis-Wiring Protection circuit is required for DeviceNet that it protects devices under power failure such as accidental connection of the Vbus+ signal to the Vbus- terminal and loss of Vbus- connection. Some transceiver may not need Mis-Wiring Protection circuit and I need to know there are the concern of SN65HVD252 or not?

Are there the reference designs of this CAN? This CAN may connect to 3.3V CAN controlller on 3.3V MCU.

Thanks and Best regards,

Loc

  • 0
    TI__Mastermind 21768 points

    Hi Loc,

    The device can survive CANH and CANL lines being shorted together or an open at either bus pin. For both cases the absolute max ratings for the pins are not exceeded. Is that all you are concerned with?

    The TXD and S pin on SN65HVD252 are 3.3V micro tolerant. They have a VIH threshold of 2.0 volts. Also the RXD pin output voltage is typically 3.3 volts max of 3.7 volts. Therefore, all the pins that the local CAN controller communicates with are 3.3 volts tolerant.

    Thanks,

    John

     

  • 0 in reply to John Griffith
    Prodigy 180 points

    Hi John,

    I have a concern about pins S and VREF. How do I connect these pins to 3.3V MCU?

    Mis-wiring protection is extracted from DeviceNet spec as below pictures

  • 0 in reply to Loc Nguyen Huu
    Prodigy 180 points

    Mis-wiring protection circuit is attached in word file.1541.mis-wiring protection circuit.docx

  • 0 in reply to Loc Nguyen Huu
    TI__Mastermind 21768 points

    Hi Loc,

    The VREF pin is a VCC/2 voltage reference made for common mode bus stabilization. It is used in what is known as "Split Termination". Please see picture below.

    The S pin for placing the transceiver in either silent mode or normal mode will just need to be connected to a standard GPIO pin. It will need to be pulled high (VIN > 2.0 volts) for silent mode and low (VIN < 0.8 volts) for normal mode.

    In terms of the mis-wiring concern, since the SN65HVD252 is not able to withstand negative voltages greater than 0.3 volts, it looks like you will need to implement the protection that the DeviceNet Spec is calling out.

    Thanks,

    John