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XTR117 with 9V power supply

Roser Torrent
Prodigy 40 points
Other Parts Discussed in Thread: XTR117, XTR111, XTR110

Hi,

I'm testing the following circuit, and I have a problem. I have soldered this circuit without R9, and in that point (Out1) I have the correct signal amplified.

After that point, in R19 I don't have any signal, only an offset voltage in 4.5V. (you can see there is a differential voltage, V+ = 9V, -V=0V and Vgnd = 4.5V).

My power supply, in XTR117 (pin 7) is 9V. Is that a problem? In the datasheet of XTR117 says that the voltage input can be between 7.5V to 40V, if I put 9V, the Rin (ie R7=20K) must be lower of higher than 20K or this parameter? either haven't to change although the power supply is lower than 24v?

Is there any relation between Rin and Power Supply?

Thanks,

  • 0
    Guru 21975 points

    Roser,

    I believe that you have misunderstood the function of the XTR117. This device is intended to operate as a remote two-wire transmitter. All current powering input circuitry is intended to be derived from the Vreg pin (8) of the device and returned to the Iret pin (3). The Iret pin must be allowed to float with respect to the output pin (4). It is not intended to be used with circuitry that is powered from external power supplies. All power is derived from the two-wire connections at pins 4 and 8.

    The way in which you are forcing the voltage on pin 3 with IC1 will not allow the XTR117 to function properly.

    I believe that you need a so-called three-wire transmitter IC. The XTR110 and XTR111 perform this function. Given the AC nature of your signal, I believe the XTR110 would be the best choice. Minimum operating voltage of this device is 13.5V. Do you have a voltage greater than 12V in your system?

    Regards, Bruce.

  • 0 in reply to Bruce Trump
    Prodigy 40 points

    Bruce,

    Thank you very much for your answer, now I understand correct running of the XTR117. I need to supply my circuit in 12V, therefore I'll try develop another current loop circuit, maybe a "manual" circuitry.. with an operational amplifier, TRT, source current, etc...

    Regards, 

    Roser