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Regarding xtr105

Motti Gill
Prodigy 10 points
Other Parts Discussed in Thread: XTR105

Hi everyone,

I am using XTR105 chip for my application. I have selected it for the temperature range -100 to +200deg. celcius for my application. I have managed to get the circuit working but when the terminals of the RTD is left open it consumes 27mA of current as it says on the data sheet. This is good for detection of a disconnected RTD terminal. But if we are not using the device, then the terminals are left open forcing Xtr105 to consume more current. I can short the RTD terminal with a value equal to Rz which will drop Vin to zero and so Iout = 4mA and if Vin goes negative Iout will be minimum 2.2mA as given in the datasheet.

My question is how low can Vin be?  In my application Vin = -48mV if I am using PT-100 and Vin = -480mV if I am using PT-1000. In other words if I short RTD connection terminals with 0 ohm resistance, will it affect the chip?

Regards,

  • 0
    TI__Mastermind 25160 points

    Motti,

    We are currently looking into this and will get back to you shortly.

  • 0 in reply to Chris Featherstone
    TI__Guru 63915 points

    Motti,

    This is the exact same question a user "Mister Lei" posted on Friday morning to an internal TI amplifier forum.  Perhaps you contacted your local TI sales team and they posted the question as well.  Here was my response on the internal thread:

    Hello Lei,

    It is okay to short the RTD terminals so the XTR will only output 2.2mA instead of 27mA if the RTD was left open.  In your final application if the RTD is shorted you may use the 2.2mA as an indication of that failure mode.

    Regards,
    Collin Wells
    Precision Linear Applications