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  • TI Thinks Resolved

SN65HVD82: SN65HVD82 noise issue

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Replies: 3

Views: 569

Part Number: SN65HVD82

Hi Team,

I am Shawn, AE of MCP, I am rotating in south China FAE Team.

We meet an issue of RS485, customer use SN65HVD82 to communicate with USB 485 debugger, the wire is only 1 meter. SN65HVD82 is on the board of inverter, and the inverter is powered by an isolated AC/DC power supply, USB debugger is connect to PC. It's worth noting that SN65HVD82’s GND and USB’s GND are not connected to each other, Only two lines of A and B are used in communication.

The following is the customer frequency converter control panel, the red arrow is the 2 wire connector of PC USB, and the red circle is the 485 transceiver chip.

We tested 4 chips, SP483, SN65HVD82, THVD1500, THVD1550, and they are tested under the same conditions, below are the test results:

  1. SP483 connects to PC USB

                 

                             no communication                                                                   with communication

       2. SN65HVD82 connects to PC USB

                

                             no communication                                                                           with communication

        3. THVD1500 connects to PC USB

             

                            no communication                                                                             with communication

        4. THVD1550 connects to PC USB

             

                             no communication                                                                      with communication

        5. Below are the waveforms on the condition of THVD1550 doesn’t connect to PC USB and THVD1550 connects to PC USB but on communication.

            

The customer is using SP483 currently, we want to use SN65HVD82 to replace it, but from the test results, it has noise issue, also THVD1500 and THVD1550 do, now we have two questions:

  1. We test SN65LBC184 before, it works well like SP483, on noise issue, so what is the different between SN65LBC184 and SN65HVD82, THVD1500, THVD1550?
  2. How does the noise come into being?

Could you help to give some comments about this?

Thanks very much.

Best Regards,

Shawn Nie

 

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