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XTR117: Designing Active 4-20mA Transmitter

Harish Singh
Intellectual 995 points
Part Number: XTR117
Other Parts Discussed in Thread: MSP430FR4133,

Hi,

I'm already have designed products with XTR117 + MSP430FR4133 with loop power, and they are working perfectly on various sites.

Now I'm designing a product with inbuild SMPS, can power to pulse transmitter (such as NAMUR) and can give an active 4-20mA current. I'm having trouble i.e. the circuit is not giving the output.

My circuit is attached.

Thanks & Regards,

Harish

  • 0
    TI__Mastermind 23050 points
    Hi Harish,

    Can you please elaborate on the behavior you are seeing on the output? It is a little difficult to tell from the schematic above, but it looks as though you may have an issue with your IRET ground and loop supply ground not being properly isolated. I'm not sure what the ground of the TPS78230 is, but if the supply to the microcontroller is generated from Vcc2, which shares a ground with your loop supply, then you will need to isolate the PWM signal from the XTR to prevent IRET from being forced to the loop supply ground. Here is an article by my colleague, Collin Wells, that explains this further: e2e.ti.com/.../two-wire-4-20ma-transmitters-background-and-common-issues-part-4