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RCV420 short circuit in its inputs

Pascal Corniglion1
Prodigy 10 points
Other Parts Discussed in Thread: RCV420

Hi,

I don't find any information in the datasheet of the RCV420 about the possible short circuit of the side of the current loop.

Is it destructive for this component ? So, we must use a particular protection.

I don't find any information about its current consumption. Did you have this informations, nominal and extrem with the temperature.

Many thanks,

Best regards,

Pascal

  • 0
    TI__Guru 64125 points

    Hello Pascal,

    I believe you're asking that if the current-loop output wires are shorted will it damage the RCV420.  Is that correct?

    If so, then the question depends on whether the RCV420 is receiving inputs from a 2 or 3-wire transmitter.  

    For a 3-wire transmitter, shorting GND to the input pins 1 and 2 or pins 2 and 3 will not damage the RCV420, it will simply cause a 0V input which will cause the RCV420 to output the minimum output voltage that it's configured for.  If the input is shorted to V+ then it will cause a very large current to flow from V+ to GND through the 75 Ohm input sense resistor of the RCV420 of input current I = (V+ / 75 Ohms).  This may cause the supply that powers V+ to droop or shut down if it can't provide the required current.  If the supply can provide the current then it could damage the RCV420 if the input current exceeds the absolute maximum value of 40 mA.  

    For a 2-wire transmitter, shorting the wires will place the V+ voltage on the 75 Ohm sense resistor like the 3-wire case and the same over-current concerns apply.  

    Unfortunately without getting fancy there aren't any simple ways to prevent this condition from causing issues other than providing some extra series resistance in the loop.  

    Current consumption for the RCV420 is typically 3mA, max 4mA, and is listed in the "Power Supply" section of the specification table.  We do not provide a maximum specification for the quiescent current over the full temperature range.