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SN75176B: SN75176B is damaged

caglar pasli1
Prodigy 60 points
Part Number: SN75176B
Other Parts Discussed in Thread: THVD1520

Hi, 

We have designed Ethernet to RS485 converter. 

We have connected 4 slave devices on one port, 4 slave devices on the other port. 

After the devices is working for a while, one port on our device is damaged.

After that, all of the slave devices is connected the other port on our devices, and after for a while this port is also damaged.

Can SN75176B be fake?

  • 0
    Guru 316690 points

    This sounds as if the device gets damaged by overvoltage or overcurrent coming from the bus. This device handles transients only up the limits specified in the datasheet.

    Why did you choose the SN75176B? The THVD1520 is more robust (and cheaper, and uses less power). Also see sections 9.2.1.5, 9.2.2, and 11 in its datasheet for suggestions for additional protection.

    Fake devices are possible (and in certain cases, likely) if you do not buy from TI-authorized distributors. If you did buy from a TI-authorized distributor and suspect a fake, see this page.

  • 0 in reply to Clemens Ladisch
    Prodigy 60 points

    Thank you for your advice. I will try to change the SN75176B to THVD1520. 

    I have a question for the damaged. 

    As you know, there are two separately RS485 port. But there is no isolation between each other. 

    And the different devices is connected to these ports without gnd connection. Only A and B wires are connected. 

    Does this make potential difference between the ports? Does this issue create the problem?

  • 0 in reply to caglar pasli1
    TI__Mastermind 25705 points

    Yes, the transceiver ground is respected to the local one, which means there might be ground potential difference between the ports. You can measure the difference to see if it's within the range of the device (-10V to 15V).

    Regards,

    Hao