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MSP430F5438A: External Reference for ADC12

Rowshon Munny
Intellectual 390 points
Part Number: MSP430F5438A


Hello,

Anyone, please help me understand how can I use an external Voltage source as a reference for ADC12. I am using the MSP430F5438A E.board. I went through the datasheet but don't understand clearly. If I understand correctly in ADC12SREFx I have to select 010b = VR+ = VeREF+ and VR- = AVSS for my purpose. For this configuration, I have to physically connect the required voltage at pin 5.0 and GND at 5.1. Please correct me if I'm wrong. Also I would like to know about configuration 000b = VR+ = AVCC and VR- = AVSS for ADC12SREFx . How the values for AVCC and AVSS decide here? If there is any documentation on how to configure the registers overall and the physical connections required for a working ADC (with external reference voltage) please share. I am trying to get data from a sensor and for the purpose, I need a reference voltage higher than 2.5V which I found I can select as the highest internal reference. 

Thanks,

Rowshon.     

  • 0
    TI__Genius 10860 points

    Hi Rowshon,

    I understand that you've already read the device datasheet and the family User's Guide so that should be good as a basis.

    The next step to verify your understanding and get some answers to your questions could be to have a look at the code examples we provide, there are also some ADC12 examples that show how to use the external reference.

    Please have a look the the software examples included in MSP430Ware and let me know in case there are more open questions after that.

    Best regards,

    Britta

  • 0 in reply to Britta Ruelander
    Intellectual 390 points

    Hello Britta,

    Thanks for your response. So msp430x54xA_adc12_05.c answers how to apply the external reference. But my other question was How the values for AVCC and AVSS decide? I don't find any explanation of it in those examples but the examples use AVCC and AVSS. Am I missing something from datasheet or user guide? And what is the maximum value of voltage I can apply for external reference? 

    Thanks,
    Rowshon.

  • 0 in reply to Rowshon Munny
    TI__Genius 10860 points
    Hi Rowshon,

    you'll find the recommended values for the supply voltages AVCC and AVSS in the device datasheet. In the absolute maximum ratings section you'll also find the absolute maximum voltages you can apply even though those are not recommended and will have consequences on the device lifetime and operation. Thus, please follow the recommended values for supply voltage.

    Best regards,
    Britta
  • 0 in reply to Britta Ruelander
    TI__Genius 10860 points
    Hi Rowshon,

    as I didn't hear back from you I assume that the issue has been solved on your end.
    Please note that I'm closing this thread but that replying back to it will re-open it if needed.

    Best regards,
    Britta
  • 0 in reply to Britta Ruelander
    Prodigy 140 points
    Sorry for late reply. Yes my issue resolved.

    Thanks.

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