supply voltage vs. output/input voltage on DACs and ADCs

Hello,

I am interested in using AD5686R and AD7682 for a lightweight analog data acquisition system. Right now, I am thinking about how to properly power these devices. One of my design constraints is that the device must be powered by a wall wart with a +5 volt  output. I was thinking that I would pass this through a LDO regulator to get a clean supply rail. However, even with the lowest dropouts, the best I can do is get ~4.8 volts to the supply pins of the converters. According to the data sheets, the converters must have the following voltage supply ranges:

AD5686R: 2.7-5.5 volts

AD7682: 2.3-5.5 volts

so, I am right in the sweet spot with my regulated 4.8 volt supply.

Here is my question: The AD5686R generates a internal 2.5 volt reference and, using  a gain factor of 2, allows the chip to have a 2*VREF = 5 volt swing on its output pins. If I use the device in this mode while only supplying 4.8 volts, will I be limited to a 4.8 volt output instead of the full 5 volt range? Is this also the case for the AD7682 in terms of the swing of its inputs? If so, I suppose I can use an external reference voltage.

Thanks.

-jon

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  • 0
    •  Analog Employees 
    on Mar 11, 2013 2:38 PM

    Hi Jon,

    You can supply the device using a 4.8 V supply but you will be limited to 4.8 V at the output if using the internal reference and a gain of 2..

    If you are looking at using an external reference then please use the AD5686 and not the AD5686R..

    The input and output ranges will be limited by supply.

    Regards,

    Padraic

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  • 0
    •  Analog Employees 
    on Mar 11, 2013 2:38 PM

    Hi Jon,

    You can supply the device using a 4.8 V supply but you will be limited to 4.8 V at the output if using the internal reference and a gain of 2..

    If you are looking at using an external reference then please use the AD5686 and not the AD5686R..

    The input and output ranges will be limited by supply.

    Regards,

    Padraic

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