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Need low cost replacement circuit for XTR101

Prodigy 160 points

Replies: 7

Views: 1052

Hello TI,

We are using XTR101 chip for RTD to 4-20mA current conversion. We are almost using 1k+ volume per month & we have 5k stock.

The cost of the chip we are getting around 560 Indian rupees for 1k volume. The performance, reliability & repeatability of the chip is excellent. Now we are try to reduce the price of the components. So can anyone suggest a best replacement of XTR101 circuit with lower cost. 

Specification : RTD input 0-150°C to 4-20mA current output. Supply 24V.

Thanks in advance

Regards

Udhay

Udhay
Hardware Design Engineer
www.precimeasure.com
  • Hello Udhay,

    Please take a look at the XTR105, XTR112, and XTR114.  The XTR105 is an updated version of the XTR101 with some performance and linearity improvements.  It's also listed at about 1/2 the 1k pricing of the XTR101 on ti.com.  The XTR112 and XTR114 are meant for PT-1000 and PT-5000 sensors so if you change from a PT-100 later consider those ICs as well.

    http://www.ti.com/lsds/ti/amplifiers-linear/4-20mA-conditioning-products.page?paramCriteria=no

    Regards,
    Collin Wells
    Precision ADC Applications

  • In reply to Collin Wells:

    Dear Collin Wells,

    Thank you for the reply. I will try to use the XTR105 for my application.

    Can we use the XTR108 for the same application? Do we required a microcontroller to operate the XTR108? what is the purpose of using EEPROM in addition with XTR108

    Udhay
    Hardware Design Engineer
    www.precimeasure.com
  • In reply to udhay kumar:

    Hello,

    Yes, the XTR108 works very well for RTD applications, there are several examples given in the Application section of the product datasheet.  The XTR108 is meant to operate stand-alone with only an EEPROM containing device calibration settings that are determined during factory calibration.  You will need a microcontroller or some other type of digital interface to initially program and calibrate the system and load the correct coefficients into the EEPROM, but once deployed the XTR108 will read from the EEPROM on startup without an external microcontroller.

    I suggest you consider acquiring an XTR108 EVM which can be used to gain better understanding of the XTR108 functionality and the software requirements to interface with the device.

    http://www.ti.com/tool/xtr108evm-usb?keyMatch=xtr108&tisearch=Search-EN

    Regards,
    Collin Wells
    Precision ADC Applications

  • In reply to Collin Wells:

    Dear Collin Wells,

    Thank you for your valuable reply. Now I'm going with XTR105 chip for my ongoing design. I will consider XTR108 for my future application.

    Now i started my design with XTR105. Unfortunately I can't find sample of XTR105 from TI list. If you can, please verify my circuit diagram for my requirement. The circuit diagram & calculation results are attached.

    This circuit works in high surge environment (very near to HV transformer in sub-stations). If you can, please suggest a high level protection circuit for the system. We are already facing problem with XTR101 circuit from surge & lightning.

    Udhay
    Hardware Design Engineer
    www.precimeasure.com
    XTR105 CIRCUIT.pdf
  • In reply to udhay kumar:

    The calculation work sheet is here...

    Udhay
    Hardware Design Engineer
    www.precimeasure.com
    XTR105 CALCULATION.pdf
  • In reply to udhay kumar:

    Hello,

    I verified the values and connections on your schematic and it looks good to go.  I've also attached an Excel calculator for your benefit that shows basically the same answers that you arrived at for the resistors in the circuit. 

    8267.XTR105 Resistor Calculator.xlsx

    Regarding your request for protection circuitry, please read through and implement the external protection components used in: http://www.ti.com/tool/tipd126?hootPostID=b095af6eb6bbcbed6cff552c47321ef7

    That design uses the XTR117 as the 4-20mA driver but the same protection circuitry shoud prove effective for the XTR105 output as well.

    Regards,
    Collin Wells
    Precision ADC Applications

  • In reply to Collin Wells:

    Hi, Thank you very much. I will go with the design.

    Udhay
    Hardware Design Engineer
    www.precimeasure.com

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