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XTR110 Failure

Other Parts Discussed in Thread: XTR110

Hello there.

I need some help in troubleshooting a problem we are having with the XTR110 V to I Transmitter.

We are experiencing repeated failures in Production of an XTR110 current source.

This design has been in production for several years now and the problem is not new.

The failure occurs at a constant rate, maybe 1%, but it causes us to scrap an entire board after much testing/calibration, so it is a costly problem.

The XTR110 circuit is configured for 0-5Vin and 0-20mA out as shown within Fig-1 of the datasheet.

The failure exhibits two features:

    1) a loss of FET drive control (pin14 pegs at a low voltage, ~2V);

    2) what appears to be a high internal current (part gets hot).

Whatever has ocurred, it appears to be a catastrophic failure.

The input circuitry appears to be unscathed and behaves appropriately - monitoring the output of pin8 gives expected voltages over the full Vin range.

The circuit was designed to operate at 12V, although the Vcc min specs at 13.5V.

Burr Brown was consulted at the time of the original design (10 years ago), and the green light was given for 12V operation.

Also, the circuit operates at a constant 73C temp.

Since the TI acquisition, has the XTR110 undergone any die revisions?

At the given operating parameters, 12V & 73C, are there any conditions that would cause the failure described?


Mark Abraira


  • Hello Mark,

    First, we can't guarantee the product performance when operated outside of the specified datasheet limits. That said, please help answer a few questions and we'll go from there. 

    Does the failure occur during production or once it has been out in the field?  If these are field returns, what is the typical product life before failure?  Is it possible that a transient/surge event could be causing electrical overstress to the XTR? Could you please provide a schematic for your system for us to review?

    The datasheet recommended limits are almost always specified with some guardband such that the product will continue to meet the required performance specifications over process variation and product lifetime.  Using the product by over a volt less than the recommended limits may have been fine in some production lots but may not be okay in others as the process shifts over time which may explain the issues.

  • Collin,

    Thanks for the response.

    These failures are occurring in Production test.

    I am not aware of any field failures that identify the Analog Brd as a cause.

    I have attached the Analog Brd schematic and a picture that shows the thermally-controlled sub-assy in which the Analog Brd resides. It is the right-most PCB on the ribbon cable within the Hot Zone Assy.

    So far, I am thinking the problem has to do with our operating condtions (12V @ 73C) while switching the P/S to the XTR110 circuit on/off during test. I am still gathering data from Production.

    Failures are ocurring after boards are built into sub-assemblies, have passed prior test milestones spanning days, and reside in an ESD controlled test environment.

    The XTR110 circuitry is not directly accessible to hands-on events, like ESD, involving the sub-assemblies.

    But, what are the absol max limits on those FET drive pins? I will look more closely at that.

    I am wondering if there are events at our operating conditions that might cause the described failure.

    Something like the DS page 6 note about the input voltage going below -0.5V, although the input OpAmp seems to function fine after the FET drive has permanently checked out.

    Let me know if you need more info.


    Mark Abraira1832.801-0048-02_b.pdf

  • Hello Mark,

    Thank you for the detailed information. Please confirm that the XTR110 failures occur during a test which cycles the +12V power while operating at +73C.

    The FET drive pins have absolute maximum voltage ratings of VCC and GND, and the current that flows from VCC to PIN 1 can't exceed 40mA. 

    We don't think that the issue is coming from the input side, because the LM302A connected to the input appears to be powered from +5V and GND.  Therefore, it can't produce voltages outside of +5V or GND which should not harm the XTR110.

    Our guess is that the issue is caused from some sort of transient voltage produced by the load when the power is cycled on and off.  We believe the load is connected to the "TCD Therm Com" net.  If so, a positive voltage transient from the load would cause the IRF7416 internal drain-to-source diode to conduct which could cause electrical overstress to pins 1 or 13 based on the voltage applied. Also, if the transient has enough current it could damage the resistor between pin 1 and VCC. Either condition would cause irreversible damage to the XTR110.



    Our recommended solution would be to place a 12V transient voltage suppressing element and 10 - 100nF capacitor directly on the "TCD Therm COM" pin to GND.  Then place a 15 Ohm resistor in series with the output terminal and the XTR110 output. 

    An example of a very well protected 3-wire analog output simiilar to this design can be seen in TIPD153 

    If this is being deployed in an industrial environment either now or in the future we would recommend implementing a very similar circuit.  Less rugged environments will probably do fine with just the TVS diode and capacitor directly on the output with the 15 Ohm series resistor.  Since you haven't experience field failures in several years of operation, the reduced circuitry is likely more appropriate for your application.

    Some circuitry is sensitive to capacitors placed on it.  Please be sure that the load side of the "TCD Therm COM" pin can tolerate capacitive loads.  If it is an input pin this will likely not be an issue, but if it's an output it could cause issues.

    Keep in mind the failures could simply be related to operating the device outside of the recommended operating voltage range at +73C while cycling the power on and off.  However, since the failure doesn't occur often try adding the protection components and see if the failures stop occuring.


  • Colin,

    Thanks for you input.

    We have been able to quantify ESD events on the Production floor.

    We also have confirmed that an ESD event can penetrate into the sub-assembly and to the current drive circuitry.

    We have not yet been able to cause an XTR210 failure, since my time on this effort keeps being interrupted, but I will get back to it.

    We sent TI a few failed part for analysis, and I am hoping that they will be able to confirm evidence of ESD damage.


    Mark Abraira

  • Hi Mark,

    Great work investigating this issue.  Please let us know the results of your failure analysis and if we can do anything to help.