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SN55LBC172 vs SN65HVD10 driver

Barry Allred
Prodigy 40 points
Other Parts Discussed in Thread: SN65HVD10, SN55LBC172, SN65HVD1787, SN65HVD1793

I recently redesign a circuit board for obsolescence and among other things replaced the RS-485 drivers and receivers with a transceiver.  The previous design used SN55LBC172 drivers, the new design uses SN65HVD10.  During a critical design review our customer informed us that they sometimes use the hardware in a configuration that is not compliant with the EIA-485 specification (I waiting to get specifics on this environment but I know it has to do with cable length) but that original hardware worked ok in this non-compliant configuration.  They are concerned that there is risk that the driver in the new transceiver will not necessarily work in this non-compliant configuration.  We are just starting to build prototype hardware for the redesign and are looking to determine if this new transceiver will work.

I know this is a long shot but I am wondering:

Are both parts fabricated with the same process?

If so are the output buffer designs in the two parts the same?

I know they are different voltages but since these are differential outputs I don't know if that necessarily means they are different designs.

Thanks,

Barry

  • 0
    TI__Mastermind 28265 points

    Hi Barry, the SN55LBC172 is a 10 Mbps device, while the SN65HVD10 supports up to 32Mbps with very short rise and fall times. Your customer's EIA-485 non-compliant application might include the use of unterminated bus lines. Whatever they spec. discloses, aim for a device with lower bit rate and longer transition times, particluarly when operating at low supplies (i.e.3.3V). I really would suggest for that non-compliant issue to use our high-common-mode transceivers but all of them require a 5V supply such as the SN65HVD2x family, or the SN65HVD1787 (half duplex) or SN65HVD1793 (full duplex) 

    Is there a way you could get to 5V?

    Please let us know what the non-compliance issue consists of.

    Best regards,

    Thomas