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THVD1450: loss data issue with THVD1450

Part Number: THVD1450

Hi Team,

Customer uses THVD1450DR in their system to communicate with PSU(ST3845 in side) by 2M cable. 

Here is the system block,  Customer found losing data issue at THVD1450 side.

Could you help to check the block and give some suggestions?

Thanks.

  • Hi Oliver,

    It sounds like THVD1450 is unable to recognize the signal coming from ST3845 in this application. This would cause apparent communication failure when THVD1450 is acting as the receiver. My initial thought is that this has something to do with the different transceivers used and the large series resistance of the system created by the blocking resistors and cabling. Taking a quick look at both device datasheets, THVD1450 specifies a larger minimum differential output voltage than ST3845 when operating at 5V Vcc and under the load presented in your schematic. This may allow THVD1450 to drive a valid RS-485 signal through the resistance presented by the series resistors and cabling through to the other node. With a lower differential output capability, ST3845 may not be able to do the same in the opposite direction. 

    To test different solutions, you may consider reducing the values of the series resistors to reduce signal attenuation in this protection circuitry. If THVD1450 is indeed successfully able to drive through these conditions, you may also consider replacing the transceiver at the other node with THVD1450 as well.

    Let me know if I've understood the situation correctly and if you have any more questions.

    Regards,
    Eric.