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SN65HVD09: Is SN65HVD09 a good choice?

Sara Jia
Expert 2975 points
Part Number: SN65HVD09

HI team,

For the differential encoder, the output signal level is RS422 level. Our industrial camera needs to receive the differential signal from the encoder and needs a differential receiver. Am26ls32 is a four channel differential receiver.

I see that there is also an RS485 transceiver with isolation on TI's official website. I wonder if the differential receiver of the encoder needs to choose the isolation scheme?

Can we choose a common differential receiver and then add an optocoupler for isolation?

I also see that there is a direct use of optocoupler to receive the differential encoder signal, and there is no use of differential receiver, so what should be paid attention to in this design?

Pls give me some recommendation on this issue,or give me the replacement P/N for Am26ls32?

Thanks 

  • 0
    TI__Guru 62920 points

    Hi Sara,

    Whether or not isolation is needed is an application-level decision.  Typically it is used in cases where the nodes need to communicate across substantially different power domains (for example, if the voltage differential between the ground references at each nodes exceeds the common mode rating of the differential transceivers used) or in cases where containing potential high-voltage faults is important (either to protect more sensitive/expensive circuitry or a human operator).  If this is not the case, then a design could function without isolation.

    When isolation is used, it can be done either via an integrated isolated transceiver (such as these devices: http://www.ti.com/isolation/isolated-interfaces/rs-485-transceivers/overview.html), a regular non-isolated transceiver paired with a digital isolator (such as these: http://www.ti.com/isolation/digital-isolators/overview.html) or a regular non-isolated transceiver paired with something like an opto-coupler.

    I wouldn't generally recommend interfacing the differential signals directly to an opto-coupler since these would not be designed to be compliant to a common physical layer standard like RS-422 or RS-485 and as such may not meet requirements for specifications like the input sensitivity.

    Regards,
    Max

  • 0 in reply to Miguel Robertson
    Expert 2975 points

    Hi Max,

    Thanks.

    BR

    Sara