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SN65HVD3088E: Not compliant to TIA-422-B?

Raphael Strebel
Prodigy 60 points
Part Number: SN65HVD3088E
Other Parts Discussed in Thread: SN65ALS176, THVD1550, THVD1500

Hello,

I want to use SN65HVD3088E for a combined RS485 and RS422 application. The data sheet states compliance to TIA-485-A and TIA-422-B, but supports maximally -9V to +14V on pin A and B. Though, the TIA-422-B standard requires a maximal single ended voltage on pin A or B of +/-10V (see Figure 11 in section 4.2.2).

The same issue applies also to other TI transceivers (e.g. SN65ALS176).

Why is it stated in the data sheet that it conforms to the  TIA-422 standard (Mentioned under 10.2.1.4 of the data sheet)?

Best,

Raphael

  • 0
    TI__Guru 62920 points

    Hi Raphael,

    That's a good catch - while TIA-422 specifies a common-mode range from -7 V to +7 V, the single-ended receiver input voltages are specified to +/- 10 V to accommodate some additional differential signaling component.  In order to fully cover the entire possible voltage range, I'd recommend using a device specified with a wider range like THVD1550 (which is a pin-to-pin functional equivalent to SN65HVD3088E with improved performance) or THVD1500 (if lower data rates are used).

    Regards,
    Max

  • 0 in reply to Miguel Robertson
    Prodigy 60 points

    Hi Max,

    So these transceivers are not compliant to TIA-422 even if the sentence "To comply with the RS-422 and RS-485 standards, .."  insinuates it?

  • 0 in reply to Raphael Strebel
    TI__Guru 62920 points

    Raphael,

    Yes, it would seem that the requirement in the absolute maximum table for bus pin voltages to be higher than -9 V conflicts with the TIA-422 specification's requirement to support an applied voltage of -10 V.  Within the specified operating range of the IC, though, the performance would align with TIA-422 requirements.

    Max