AD7734_conversion result

Hello

I'm using AD7734.

It's use under the following conditions.

 ・Single conversion(Dump mode)

 ・Range 0 V to +5V

 ・16 Bits

 ・CLAMP = 0 

In this case, may conversion result of "SIGN=1 & OVR=0" be got?

Please tell me.

Best regards

Parents
  • 0
    •  Analog Employees 
    on Dec 17, 2019 6:19 AM

    Hi,

    If sign is 1 then it indicates that the input is negative and with nominal voltage range of 0 to 5V a SIGN=1 which means a negative voltage value is always outside range so OVR=1.

    May I know what is your application? And why do you ask this? Have you got this results on your setup? If you could share to us your setup and register settings then that would be helpful.

    Thanks,

    Jellenie

  • Hello JellenieR

    Thank you for the answer.

    sorry,I can't speak application. Because this site is open source.

    The reason why I asked this question is that I was able to read SIGN=1 & OVR=0 when I saw the output waveform.

    It is a value of the status register at that time.

    I confirm it about the procedure of setup data.

    I come back to this site afterwards.

    After the confirmation, I post it on here again.

    Best regards

  • +1
    •  Analog Employees 
    on Dec 18, 2019 3:23 AM in reply to baggio

    Hi,

    May I know what is your input voltage? 

    Please confirm the register settings especially the channel setup registers. If you can read back this to confirm that the nominal voltage range is set to 0 to +5V.

    Thanks,

    Jellenie

  • Hello JellenieR

    Thank you for the answer.

    The input level is 0V.

    I write in it and show the procedure.

     Address 0x00  ←0xFF

                 0x30  ←0xFF

                 0x28  ←0x03

                 0x38  ←0x18

     I confirmed the set point

    Address

                 0x38  ←0x58

                outputdate  ←0x00

    I will include a set point from now on and want to reconfirm.

    In addition, please tell me if you have any questions.

    Best regards

  • 0
    •  Analog Employees 
    on Dec 19, 2019 3:15 AM in reply to baggio

    Hi,

    When you input 0V to AIN0, Does your BIAS0 connected to 2.5V? If you can also probe the inputs to confirm that the input is at 0V. Because if it is negative, the result will always be 0 code for any negative input voltage value since the part is configured to accept only unipolar ranges (0 to 5V). However, if this is the case the sign bit and OVR bit should both be set.  

    Yup reading back the set point is worth doing to confirm that you have written correct values to the register. Can you also try to read back the ADC ZS cal register to confirm that the sign bit is 1?  

    Can you try the following steps?

    After powering up the AD7734, can you reset the part by writing 32 ones to ensure that all registers are at their power on/default values. You can then configure the part by writing to the registers. Try to read back the registers to ensure that the correct register values was written to the part. If everything works fine, you can now initiate a single conversion mode by writing the 0x3858, wait for RDY pin to go low (probe to check that it goes high when the single conversion is initiated and returns low when a conversion is available). If RDY pin goes low, you should now attempt to read the status+data register and ZS cal register to confirm.

    Thanks,

    Jellenie

Reply
  • 0
    •  Analog Employees 
    on Dec 19, 2019 3:15 AM in reply to baggio

    Hi,

    When you input 0V to AIN0, Does your BIAS0 connected to 2.5V? If you can also probe the inputs to confirm that the input is at 0V. Because if it is negative, the result will always be 0 code for any negative input voltage value since the part is configured to accept only unipolar ranges (0 to 5V). However, if this is the case the sign bit and OVR bit should both be set.  

    Yup reading back the set point is worth doing to confirm that you have written correct values to the register. Can you also try to read back the ADC ZS cal register to confirm that the sign bit is 1?  

    Can you try the following steps?

    After powering up the AD7734, can you reset the part by writing 32 ones to ensure that all registers are at their power on/default values. You can then configure the part by writing to the registers. Try to read back the registers to ensure that the correct register values was written to the part. If everything works fine, you can now initiate a single conversion mode by writing the 0x3858, wait for RDY pin to go low (probe to check that it goes high when the single conversion is initiated and returns low when a conversion is available). If RDY pin goes low, you should now attempt to read the status+data register and ZS cal register to confirm.

    Thanks,

    Jellenie

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