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XTR108

Zdenek Masek
Prodigy 40 points
Other Parts Discussed in Thread: XTR108

Hello,

is it possibble to use XTR108 without serial EEPROM ?

I suppose, that MCU connected to XTR108 will always configure XTR's registers after each power-up. I would like to use four XTRs (each with one 3-wire RTD for temperature measurement) with their SPI bus connected together and tied to MCU. I suspect that it will not be possible with EEPROM connected to each XTR because XTR doesn't have separate SPI interface for communication with EEPROM.

For completness: I will not use current output from XTR108, only voltage output (pin Vout), XTR supplied with +5V on pin Vs, pin Iret acts as GND).

Thank you for answering.....

Zdenek

 

 

  • 0
    TI__Mastermind 27715 points

    Hello Zdenek,

    Thank you for your question regarding the XTR108.

    It is possible to use the XTR108 without an external EEPROM, but as you mentioned a MCU must be used to configure the internal registers each time the part starts up.

    As for your particular application, I am unsure that your configuration will work when connecting 4 XTR108s to the same SPI bus of one MCU. I assume you wish to write the same register values to each XTR108, is that correct? I think you might experience some bus conflict errors, but I will need to investigate this further.

    Please confirm what/how you intend to write to the 4 XTR108 registers, and I will confirm whether multiple XTR108s can receive simultaneous data on a single SPI bus.

    Best regards,

    Ian Williams
    Linear Applications Engineer
    High Performance Linear

  • 0 in reply to Ian Williams
    Prodigy 40 points

    Hello Ian,

    thank you for quick reply !

    Yes, I suppose to write the same configuration at start-up to each XTR.

    I think if SPI interfaces of all XTRs will be connected together, with no EEPROM used, there should be no problem with communication - communication with each XTR will be enabled via CS of a particual XTR (i.e. four XTRs = four separate chipselects). Or is it possibble to connect chipselects all together and communicate with all XTRs at the same time ? (expecting the same configuration of each XTR as I mentioned above)

    I only suspect some problems at the power-up because XTR would try to communicate with EEPROM.......and if no EEPROM will be used....what will happen at start-up ? I didn't find much detailed information about this behaviour (using XTR without EEPROM) in datasheet........

    So, this is my concept, it is possibble that I am wrong......and it is up to you to explain it a bit to me :-)

    Thank you very much !

     

     

  • 0 in reply to Zdenek Masek
    TI__Mastermind 27715 points

    Zdenek,

    I removed the EEPROM from our XTR108EVM in order to determine the behavior at start-up, because as you have observed there is no documentation in the data sheet describing this condition. What happens is that the XTR108 attempts to read its initial values from an EEPROM, but since no EEPROM is present to drive the SDIO line voltage low, the voltage remains fixed at the digital supply. This is interpreted as code '1111 1111' in binary or 'FF' in hex.

    However, the registers of the XTR108 itself can still be written and read with no trouble. I was able to write to all registers of the device and read them back successfully.

    As for controlling four XTR108 slaves from one master SPI controller, that is no problem to implement if you have a separate CS line for each device. This will result in the best end result for your system, because during calibration you are sure to need to write different register values to each IC.

    Let me know if you have any other questions regarding the XTR108.

    Best regards,

    Ian Williams

     

  • 0 in reply to Ian Williams
    Prodigy 40 points

    Thank you a lot for practical test, Ian ! I will connect it as you wrote above.

    I have jsut one question about operational amplifier TLV237x. Does it have input protection diodes (from inputs to Vcc and to GND) ? No info in datasheet.....

     

    Thanks

  • 0 in reply to Zdenek Masek
    TI__Mastermind 27715 points

    Hello Zdenek,

    I'm glad that my test was helpful.

    I apologize, but in order to keep the forum well-organized I must ask you to re-post your question about the TLV237x input protection to a new thread. One of our op-amp experts should have an answer for you quickly.

    Best regards,

    Ian Williams