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XTR305: Externally-Configured Mode usage

Nam, Dino
Expert 6155 points
Part Number: XTR305

Tool/software:

Dear team, 

The customer would like to develop analog output(voltage and current) and analog input module(voltage and current) using 1 XTR305 device as control /OD and mode signal. 

For Externally-Configured Mode of XTR305, Can we use XTR305 for monitoring external analog input signal as analog input module?  

The main purpose is monitoring external voltage. I think monitoring for external current input signal is available using IAout port but I am not sure external input voltage monitoring is available or not. 

Please let me know your opinion.  

- ODn signal is low , M1 : high, M2 : high or low 

Thank you. 

  • +1
    TI__Guru 52796 points

    HI Dino,

    The externally configured mode allows you to use the operational amplifier (OPA), and instrumentation amplifier (IA) circuits of the XTR305 independently of each other.

    This mode allows the use the OPA with external feedback network components as shown on the block diagram below. For voltage output (in externally configured mode) you would connect IMON to a resistor to GND, and you would be able to monitor a copy of the current output of the amplfier. Alternatively, the IMON pin can connect to SET to create a precise voltage-to-current converter (current output in externally configured mode).  See below.

    In the externally configured mode of operation, the instrumentation amplifier (IA) can be used independently from the operational amplifier of the XTR305, and can be used to monitor voltages, producing an output current IAOUT.  Use an RIA resistor between IAOUT and ground to read a voltage. The gain for the instrumentation amplifier output is below.  

    Please note, the inputs of the instrumentation amplifier require a 3V headroom away from the positive and negative supply, and the output swing of the instrumentation amplifier also requires a 3V headroom from the positive and negative supplies.

    Thank you and Kind Regards,

    Luis

  • 0 in reply to Luis Chioye
    TI__Expert 6155 points

    Hello Luis, 

    Thank you for your comment. 

    For clarify, The customer want to use IA  in the externally configured mode. 

    Vin at below equation means differential input voltage of the instrumentation amplifier (IA) (VIAin+ - VINin-). Is it right?  

    Thank you. 

  • +1 in reply to Nam, Dino
    TI__Guru 52796 points

    HI Dino,

    Yes, VIN is the differential voltage IAIN+ - IAIN-.

    Keep in mind that the voltage on both IA inputs needs to be within the supply voltage range of the XTR305 at all times to prevent damage. 

    Also, the absolute voltage of both the IA input pins require a 3V headroom away form V+ and V- supply rails to keep the instrumentation amplifier working within its linear region. Please review the instrumentation input and output range specs below.

    Thank you and Regards,

    Luis