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THVD1500: RS485 A-GND and B-GND protection

Jiahui Gao
Intellectual 1230 points
Part Number: THVD1500

Hi TI team

I wonder if this circuit can satisfy that A signal line and B signal line to GND is 30V (for 30 minutes, the chip temperature does not exceed the maximum temperature).

Will the normal communication be affected if the voltage stabilizing tube is added, or will the negative pressure burn out the voltage stabilizing diode if the AB line is to the ground, or does TI have a better protection scheme?

Is this circuit right ？

  • 0
    TI__Guru 60112 points

    Jiahui,

    With both diodes helping clamp the voltage (19V for the BV-712 and 22.5V for the SMAJ15CA) on both lines, this will help keep the diodes from getting damaged themselves. Along with the PTC (limit to 0.05A) and current-limiting resistor, there's a significant amount of protection here that will limit the amount of power going into the transceiver. This scheme looks good, and I suspect your protection components would break down and cause a short to GND/open on the communication lines before the full power would be delivered to the IC pins anyway.

    Please let us know if you have any other questions.

    Regards,

    Eric Hackett