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AM26LV31E unused channel

Stefano Infante
Expert 2320 points
Other Parts Discussed in Thread: AM26LV31E

Hello,

what do you suggest to do with the three unused pins (one input, two outputs) of a channel of the quad RS422 driver AM26LV31E?

I think to tie the unused input to ground and leave the two outputs floating... is it a good idea?

Thanks

Stefano 

  • 0
    TI__Mastermind 28265 points

    Stefano,

    it's a good idea. You can make it even more robust if you connect the input via a few k ohms resistor (1k to 4.7k) to ground or Vcc. It's a precaution. Should you get nasty spikes on your reference planes (Vcc or ground) the resistor will current limit any transient currents into this open input.

    Apply the same precaution to the Enable pins of the driver and you don't have to worry about accidental latch-up issues out of the blue.

    regards, Thomas.

  • 0 in reply to Thomas Kugelstadt
    Expert 2320 points

    Thanks Thomas.

    To say it all, my application is very similar to the one you described in your article on AAJ 4Q 2011 (Extending the SPI bus for long-distance communication), so I have to double-thank you for all the hard work I copied :)

    I only had to move the isolators on the master side (because I have no room on the slave, and it's a strict single master - single slave application), find a way to carry power to the slave (that was the only hard thing left to do...), shift down to 3.3V logic and add a few control lines, as on the slave side I have an SPI digital accelerometer, rather than an ADC. 

    I used 10kohm for the Enable pins, as I have other 10kohm resistors in my design. I'll use another 10kohm for this issue. 

    Thanks again,

    Stefano