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What ADC for precise positive voltage measurement up to 5v

David Lake
Intellectual 300 points
Other Parts Discussed in Thread: ADS8326, ADS8866

I need to make a simple voltage measurement device to measure up to 5v positive only but am unsure what ADC I should use.

I need it to be accurate to at least 1mv and a 16bit resolution would be nice, the sample rate is not important.

The interface can be SPI, I2C or serial.

Leaded packages such as SOIC, SSOP or SOT-23 are preferred

Any suggestions are greatly appreciated.

  • 0
    TI__Guru**** 180961 points

    Hi David,

    At first glance, we have at least 24 parts that would fit the bill for your project.  Please use this Parametric Table search for starters.  Once you narrow down the feature set you need, let us know if there is anything else we can do to help move your project along.

  • 0 in reply to Tom Hendrick
    Intellectual 300 points

    That's exactly what I do but its not helping, how do I compare how accurate they are if that's even something I need to look for and what one is optimal for my specific application, I want something simple but there are so many to choose from.

  • +1 in reply to David Lake
    TI__Guru**** 180961 points

    Hi David,

    At 16-bits, there are 65536 'codes' associated with the conversion.  When you take your 5V source, that gives you an LSB size of ~76.3uV or roughly 13 codes/mV.  When you start looking through the possible options, you find parts with an internal reference, some that need you to apply an external reference, and others that can use the power supply of the ADC for its reference.  The applied reference is the key to accuracy in the end so you can look at things like available board space, simplicity of your BOM, etc.  Effective Number of Bits (ENOB) is another factor you can look at.  A 16-bit part from the list with ENOB of 13-bits or better should still give you better than 1mV of resolution in the end. 

    Cost and availability are factors you could consider as well.  The ADS8326 is a very simple device to use in the end and there is quite a bit of flexibility for configuring the analog input.  The SPI interface is flexible in that it allows you to use a slower SCLK which controls the sampling period.  The ADS8866 is another easy part to use and has a 'CONVERT START' input pin which you could control through a GPIO to get precise control over the actual sampling instance.  In the end, it really depends on exactly what features you need in your application.