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AD7091R-5 using internal reference

Hello,

until now I'm not able to use the AD7091R-5 with internal reference of 2,5V.
I'm sending this bytes to the AD7091-R to configure it :
\x02\x06\xC1\x01\x0F\x00
meaning config reg 0x02 is set to 0x06C1
-> CMD Mode = 1,
-> Software Reset = 1,
-> Cycletimer to default,
-> P_DOWN = 1, which should enable the internal reference.
config reg 0x01 is set to 0x0F -> All 4 channels on
then set config Reg 0x00

After this I do 8 byte reads where I can see that the conversion results are comming,
the channel index in each word counts also up, but the read values are wrong because
the internal reference is not 2,5 V (I measured around 3,2V at the REFIN/OUT pin)
Related to this "reference" the values are correct, so the AD Converter itself is ok,


But what's going wrong setting the INTERNAL REFERENCE ?

Please help!

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  • Hi Wollli,

    Apologize, I was referring on the wrong device (AD7091R). From the Table 3 of the AD7091R-5, Analog input voltage should be from -0.3V to Vref + 0.3 V only with respect to ground. Having input voltage greater than the maximum voltage will cause the diode (D3 from Figure 36) to conduct affecting the operation of the reference voltage.

    Regards,

    Daryl

Reply
  • Hi Wollli,

    Apologize, I was referring on the wrong device (AD7091R). From the Table 3 of the AD7091R-5, Analog input voltage should be from -0.3V to Vref + 0.3 V only with respect to ground. Having input voltage greater than the maximum voltage will cause the diode (D3 from Figure 36) to conduct affecting the operation of the reference voltage.

    Regards,

    Daryl

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