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XTR-ERROR-CALC: XTR305 Current Output Mode Simulation Issue (Sinking behavior & transfer function mismatch)

Marina
Prodigy 10 points

Part Number: XTR-ERROR-CALC
Other Parts Discussed in Thread: AMC3311, XTR305, TLV9002

Hello TI E2E Support team,

I am currently designing and simulating a signal conditioning circuit for an industrial data acquisition system. The main objective is to measure a high-voltage input up to 100V from an industrial machine, isolate it using the AMC3311, condition/scale it via a TLV9002 op-amp stage, and finally convert it into a current loop using the XTR305.

However, I am running into trouble with the XTR305 current output simulation in PSpice.

Current Setup & Behavior:

  • Input Stage: The high-voltage input 0-100v is scaled and isolated by the AMC3311, then converted to a single-ended 0-5v signal (V_Output) by the TLV9002.

  • XTR305 Configuration:

    • Configured in Current Output Mode with digital pins set to M1 = 0V, M2 = 5V, and OD_N = 5V.

    • Rset = 2.5k and Ros = 12.5k connected to the SET pin with a 5v reference.

    • A 250ohm load resistor (R11) connected between DRV and GND.

  • The Issue: Based on the transfer function for the current output mode,  for an input of 0-5V, the theoretical calculation should range from -4mA to +20mA. However, during the transient simulation, the output current (A_Output) is behaving like a sinking circuit running from -4mA to -20mA (or hitting convergence/saturation issues when trying to modify the resistor network).

Could you please advise on what might be causing this inverted/negative behavior or if there are specific model constraints regarding the reference configuration and supply rails for current output mode in simulation?

I have attached my current schematic and simulation files below. Any guidance would be greatly appreciated!



Project1.zip Project schematic.pdf
 

  • 0
    TI__Mastermind 30488 points

    Marina,

    Based on the fact that you are measuring -4mA to -20mA, I think you may just have your current measuring probe in PSPICE backwards.  Nevertheless, I am forwarding this post to the team that supports XTR type devices, since the problem appears to be with the XTR.

    Best regards, Art

  • 0 in reply to Art Kay
    Prodigy 10 points
    Hi Art,

    Thank you for forwarding this to the XTR team!

    Just to clarify regarding the probe: I don't think it's simply a "probe backwards" issue. If the probe were just reversed, a theoretical range of -4mA to +20mA would appear on the simulation as +4mA to -20mA (flipping the signs of each limit symmetrically).

    However, both limits are ending up negative (showing -4mA and moving towards -20mA, which means the actual dynamic response/slope of the output is inverted rather than just a measurement sign flip.
     

    Best regards,

    Marina
  • 0 in reply to Marina
    TI__Mastermind 19830 points

    Hi Marina, 

    I will take a look at your schematic and simulation and see if I can debug this on my end. I'll provide my feedback by the end of the week. 

    Thank you!

    Best regards,
    Ashley