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Original question:

RCV420: RCV240 : 0-5 v range and 2 wire mounting with ISO124

RCV420: Regarding RCV420

Joyson Patil
Prodigy 70 points
Part Number: RCV420
Other Parts Discussed in Thread: TLV2333, REF3012

Hi, I need 4-20mA input and output should be 0-3.3V. Is it possible with RCV420? Whether I need to use external circuits to bring it back from 5V to 3.3V?

  • 0
    TI__Guru 54576 points

    Hi Joyson,

    Yes, it is possible by connecting a resistor between CT (pin2) and +IN (pin 3), shorting IN- (pin1) and CT (pin 2), and using a voltage divider + opa buffer between REFOUT (pin11, pin10) and REFIN (pin12).  I will look into this in detail and provide you an schematic. Please allow me 24 hrs.

    Thank you and Regards,

    Luis

  • 0 in reply to Joyson Patil
    TI__Guru 54576 points

    HI Joyson,

    Attached is a RCV420 configuration that will accept a 4mA-20mA input and produce approx. 0V-3.3V Output. 

    It requires a 143-Ohm resistor between CT (pin2) and +IN (pin 3), shorting IN- (pin1) and CT (pin 2), REFOUT and REFOUTFB shorted (pin 11, pin 10) connected to the voltage divider + OPA buffer to REFIN (pin 12) as shown on the  schematic.

    Thank you and Regards,

    Luis

  • 0 in reply to Luis Chioye
    Prodigy 70 points

    Dear Luis, thanks for the design. In our present design we do not have +12V & -12V supply. Is it be possible with +5V supply. We have 24V supply also.

  • 0 in reply to Joyson Patil
    TI__Guru 54576 points

    HI Joyson, 

    The RCV420 requires bipolar supplies so it will not work without a negative supply.

    You could easily build a discrete 4-20mA receiver using a dual amplifier and reference.  The example below using the dual amplifier TLV2333 and REF3012 powers from a  unipolar +5-V supply, accepts a 4-20mA input and produces a +100mV to +3.25V voltage output. 

    Thank you and Regards,

    Luis