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ADS1013: Determining Full Scale Range (FSR)

Richard Leath
Prodigy 240 points
Part Number: ADS1013
Other Parts Discussed in Thread: LM4040, ADS1014, ADS1114

I'm planning to use the ADS1013 in a new design.  I will ground AIN1, and connect my single-ended signal to AIN0.  My input signal range is 0.3V to 3.5V and it is very slow.   It is not clear to me what the FSR will be.  Is it dependent on the Vdd?  I plan to use 4.096 (from an LM4040) as Vdd, but I could change that to get best resolution.

Since AIN0 will always be positive with respect to AIN1, will I lose half the range of the ADC?  

Thanks,

Richard Leath

  • 0
    TI__Mastermind 22365 points

    Hi Richard,

    welcome to our forum and thank you for your interest in ADS1013.

    The ADS1013 does only offer an input voltage range of +/-2.048V because it does not have the PGA capability. Means you could only measure signals up to 2.048V in your case. I believe the datasheet may not do a great job in explaining that. I am sorry for that.

    You would have to use ADS1014, where you should then select an input voltage range of +/-4.096V. That way you could measure a signal up to 3.5V when using a supply which is VDD >=3.5V.
    It does not matter for the performance if your supply is 3.5V, 4.096V or 5V.
    As long as your supply voltage is larger than the FSR, the FSR is independent of the supply. But if you for example use a 3.3V supply and select an input voltage range of +/-4.096V you could only measure signals up to 3.3V. Means you cannot make use of the whole code range.

    You are also correct, that when you only use the positive FSR (AIN1=GND) , you will only make use of half of the code range of ADS101x.

    The good thing is ADS1013 and ADS1014 are pin-compatible.
    And in case you would need more resolution, you could upgrade to the pin-compatible ADS1114.

    Regards,