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ISOW1432: RS422/485 Isolation

Ade Sanusi
Prodigy 10 points
Part Number: ISOW1432
Other Parts Discussed in Thread: , ISO1432, ISO1412DWEVM, ISO1452, ISO1412

We’re looking to implement a design for a full-duplex asynchronous communication using the ISOW1432.

From the ISOW1432 datasheet, Table 2 and Table 3, I'm able to put together a Truth Table and a Schematic that captures the configuration the two modes (Receive and Transmit) modes of operation.

In summary, when the driver enable pin, DE, is logic high, the differential outputs, Y and Z, follow the logic states at data input, D and the receiver is enabled when the receiver enable pin, RE, is logic low.

 

In addition to the above mentioned modes, I can’t seem to find any reference for the “Transceiver” mode of operation. i.e. the logic combinations for DE and RE_ pins. 

 

From a previous design experience, I’ve used the LTC2864 chip that configuring these pins allowed for the transceiver operation without software intervention and I was wondering if the ISOW1432 will operate just as the LTC2864 with the truth table shown in the attached image?

  • 0
    TI__Guru 55885 points

    Hi Ade,

    Welcome to TI E2E Forum!

    Thanks for detailed post describing your question.
    ISOW1432 is a full-duplex device where there are separate transmit and receive lines on the RS-485 bus. The DE and RE\ pins of ISOW1432 independently control the transmitter (driver) and receiver, respectively. Since they work independently, both the transmitter and receiver can be enabled at the same time and they both can function normal. Hence, it wouldn't necessarily a separate mode but both transmitter and receiver working at the same time.

    In summary, yes, enabling both transmitter and receiver the same time is supported and the device will work normal. Let me know if you have any other questions, thanks.


    Regards,
    Koteshwar Rao

  • 0 in reply to Koteshwar Rao
    Prodigy 10 points

    Hi Rao -

    Just wanted to thank you for the prompt response. I relayed your message to my lead/team just this morning and they're glad we can do this. We will be purchasing 4 Evaluation boards "ISOW1432DFMEVM" from DigiKey today so the software team can validate.

    Finally, to closeout our conversation/session, please see attached schematics that we plan to use in the "Tranceiver" mode and based on your response/summary, this transmitter and receiver should work at the same time.

    Thanks, 

    Ade Sanusi

  • 0 in reply to Ade Sanusi
    Prodigy 10 points

    Hi Rao -

    Please disregard the comments on the schematics as we plan to use the ISO1432. We had reached out to AD when the response from TI was a little bit delayed and since we could not verity the transceiver mode of operation initially. 

    However, after your detailed response, we plan to use the ISO1432DW chip and other isolation chips from TI. I'll be on lookout for your response to my last email.  

    Thanks,

    Ade Sanusi

  • 0 in reply to Ade Sanusi
    TI__Guru 55885 points

    Hi Ade,

    Thank you for your response and glad to know that you will be using ISO1432 for your application. I would also like to mention that we also have the EVM available for purchase on TI website, I am sharing below the link for the EVM. Please feel free to choose either of the websites as per your convenience for ordering. Thanks.

    https://www.ti.com/tool/ISOW1432DFMEVM#order-start-development


    Regards,
    Koteshwar Rao

  • +1 in reply to Koteshwar Rao
    Prodigy 10 points

    Hi Rao -

    You're welcome. I used to be a big fan of NXP and LT but TI is now my go-to due to the "one-stop" from chips, to evaluation, to Training and not to mention the power design tools, so thank you for all what you guys do. I believe my lead already placed the order on from DigiKey but I will still pass your information along. I will also keep in mind to order directly from the link you shared. 

    Very Respectfully,

    Ade Sanusi

  • 0 in reply to Ade Sanusi
    Prodigy 10 points

    Hi Rao - 

    It just occurred to us that the Evaluation Kit you shared was for the ISOW1432, that is, with the integrated DC-DC converter. Is there an evaluation board for the ISO1432? 

    Thanks,

    Ade Sanusi

  • 0 in reply to Ade Sanusi
    TI__Guru 55885 points

    Hi Ade,

    Sorry, I shared ISOW1432 because that is what in the title of this E2E post but I understand that you are planning to use ISO1432 for your application. Since ISO1412, ISO1432 and ISO1452 are all pin-compatible, we have one common EVM ISO1412DWEVM for these devices. Please find below the link for ISO1412DWEVM.

    https://www.ti.com/tool/ISO1412DWEVM#order-start-development

    If you would like to evaluate ISO1432, you can order this EVM and some samples of ISO1432. Replace the ISO1412 sample with ISO1432 and test. If you only need a few device samples for evaluation then you can also request them for free on ISO1432 product page.

    https://www.ti.com/product/ISO1432#order-quality

    Let me know if you have any further questions, thanks.


    Regards,
    Koteshwar Rao

  • 0 in reply to Koteshwar Rao
    Prodigy 10 points

    Hi Rao -

    Thanks once again for the prompt response. We'll proceed to order a couple of these evaluation board and our matching ISO1432 replacement chips.

    V/r

    Ade Sanusi

  • 0 in reply to Ade Sanusi
    Prodigy 10 points

    Hi Rao - 

    So our procurement came back indicating we can't purchase directly from TI. Apparently TI's not on our approved vendor and that makes sense since TI is a OEM. I'm trying to communicate with the procuremet office so can you please provide me your email and phone number so I can pass to the team. You will likely get an email from a Johns Hopkins University Applied Physics Lab. Also, you can email me on ade.sanusi@jhuapl.edu and that might be faster. 

    Thanks,

    Ade Sansu

  • 0 in reply to Ade Sanusi
    TI__Guru 55885 points

    Hi Ade,

    Thanks for sharing your email. I have written to you on your email in this regard, thanks.


    Regards,
    Koteshwar Rao

  • 0 in reply to Koteshwar Rao
    Prodigy 10 points

    Hi Rao –

     We were looking at the logic-compatibility or drive capability of the ISO1432 (Voh and Vol) meeting the Zync UltraScale I/O LVCMOS18 (Vih and Vil)

     Section 8.10 of ISO1432 Datasheet does mention the Voh and Vol for the “R” pin under a 5v0 and 3v3 test condition but does not give any for 1v8.

     Per our Schematics below, Vcc1 is 1v8 and we plan to perform calculations followed by an empirical/test on the evaluation board once and we’ll share data with you.

    Thanks,

    Ade Sanusi

    TI Support Case.docx

  • 0 in reply to Ade Sanusi
    TI__Guru 55885 points

    Hi Ade,

    Thank you for following up with more questions.

    VCC1 supply doesn't directly impact RS-485 bus operation and section 8.10 in ISO1432 datasheet only applies to pin R in relation to VCC1. Due to this the only specification that is affected by VCC1 in this table are VOL and VOH specs. These parameters are specified for all VCC1 values, i.e., 5V, 3.3V, 2.5V and 1.8V. Most other parameters in this table are independent of VCC1 and hence, VCC1 isn't referenced in test conditions.

    I hope this is clear, thanks.


    Regards,
    Koteshwar Rao

  • 0 in reply to Koteshwar Rao
    Prodigy 10 points

    Hi Rao - 

    My apologies for the late response. Yes! your response does help. I mean, we believe our logic compatibility and Noise Margin is within acceptable range but we're yet to interface to the ZCU which we plan to do sometimes next week. Thanks once again and have a great weekend ahead.

    Ade Sanusi