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ADM4168E RS-422 Transceiver Input Range

PBArrow
on Oct 28, 2020

I have a question regarding the input common-mode range of the ADM4168E. The datasheet says the input can swing +/-7V. However the IC is powered by a single 5V supply. Looking at the Rin spec, the condition specifies one input is at 0V, the other can swing +/-7V. So my question is, can the IC really operate with one of the Rx inputs at +/-7V? If so, is there some kind of a resistive divider and/or clamp that allows this to occur? Thanks in advance.

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    •  Analog Employees 
    on Oct 28, 2020 8:18 PM

    Hello ,

    Yes the ADM4168E is designed to operate under these conditions despite being powered from a 5V power supply.

    The receiver inputs of the ADM4168 contains high impedance passive circuitry, which can be approximated as a resistive divider + level shifter, that allows the receiver to operate across the full +7V to -7V input voltage range. The receiver inputs also have ESD clamping diodes which will turn on if the -14V to +14V absolute maximum rating of the A or B pins is exceeded.

    The setup conditions for the Rin specification in the datasheet are taken from the TIA/EIA-422 standard, which specifies that the input current and resistance should be measured with one pin at +7V / -7V and the other pin grounded. 

    Regards,

    Neil 

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