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Altera_Forum
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11 years ago

MAX10 ADC(BeMicro Max10) output value

Hi Guys,

I am testing Max10 ADC function.

When I put or assign 2.5V to AIN channel, I can't read only 4005, it should be 4095. It seems to be incorrect or truncate data.

When I put or assign 0V to AIN channel, I got 350 not 0.

When I read TSD(Temperature Sensing Diode), output is 0.

If you have any idea, please let me know.

Thanks

6 Replies

  • Altera_Forum's avatar
    Altera_Forum
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    11 years ago

    Hi dbjung,

    I had the same problem.

    The datasheet of Max10 ADC ("MAX 10 Analog to Digital Converter User Guide" pag.4) asserts that if you have a DUAL SUPPLY MAX10 FPGA you have to connect the banks where the analog inputs are placed to 2.5V power supply and you can supply an analog signal between 0V to 2.5V; instead on BeMicro Max10 all the banks are supply with VCC3P3, that is 3.3V (see the schematic of BeMicro pag. 5). This is wrong!

    Remember that on the BeMicro MAX 10 the voltage reference is correct at 2.5V;only the power supply of the banks where the analog inputs (1A and 1B ) is not correct!

    To resolve this problem I've changed the VCC3P3 supply in to 2.5V (I've changed the resistor RP4 connected to the power converter EN5319QI at pag 8 of the schematic) in such a way that the banks 1A and 1B have the correct power supply (obviously even all other banks now have 2.5V power supply).

    With this trick, you have no longer offset of 350 when the analog input is 0V and you have 4095 when the analog input signal is 2.5V.

    I've found that BeMicro has another error in timing of power sequence (it is different from that one recommended by Altera) but this doesn't matter with ADC results.

    Bye.
  • Altera_Forum's avatar
    Altera_Forum
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    11 years ago

    I could not see any correlation between die temperature and readout from TSD adc on channel 17.

    I do read a value with some fluctuation in range 3992 to 3986 (very cool to very hot , appr -20 degC ... 70 degC)

    but these is fare outside expected values.

    Any of you have TSD working on BeMicro Max 10 ?

    Thanks
  • Altera_Forum's avatar
    Altera_Forum
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    10 years ago

    I have tried the method above and it is working for the temperature measurement as well. But one thing I realize is we need to careful as the 3.3V is common 3.3V shared across the board. Some other component still using this supply and in case we change the 3.3V and some part might not well function.

  • Altera_Forum's avatar
    Altera_Forum
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    10 years ago

    Hi BennyChian,

    yes, surely some components may not work because in the way I said, the 3.3V become 2.5V but what I want to say was that the power of the bank where the analog input pin are, must be powered with 2.5V and not at 3.3V.

    Bye.
  • Altera_Forum's avatar
    Altera_Forum
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    10 years ago

    Hello

    I have the same problem with the ADC.

    Could you please tell me where I can find this VCCIO1A and VCCIO1B node on the board so I can fix this problem.

    is it possible to locate it on the actual board? (upload a photo maybe)

    I don want to change the DC converter output setting because it may lead to other problems in other peripherals

    is there any way to work around this offset in software design I mean in the HDL code for the FPGA?

    thanks alot