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ADS1262: ADS1262 internal Reference

Pranav Kumar MOudgil
Prodigy 60 points
Part Number: ADS1262

Hello Sir,

I am new to this ADC.I want run my Hall sensor on this ADC.

Then, you have provide the excel software for ADS1262.

When I m using PGA gain as 1 and Vin(-)(differential input) = 0 then it is impossible for me  to get full range  of values forhall sensor.

As minimum value Vin(-) = 0.3V when gain is 1.

So, how to solve this problem?

Pranav K Moudgil

  • 0
    TI__Guru 51081 points

    Hi Pranav,

    Thanks for your post and welcome to the forum! 

    It's the weekend, so please give us a few days to fully address this question. 

    However, it looks to me like the input range of the PGA is being violated. Some headroom from the supplies is required. Take a look at the electrical characteristics table and equation 12 in the datasheet. 

    http://www.ti.com/lit/ds/symlink/ads1262.pdf

  • 0 in reply to Alexander Smith
    TI__Mastermind 44640 points

    Hi Pranav,

    In the ADS1262 Excel calculator, the V_INP and V_INN voltages are the absolute voltages seen at the positive and negative inputs to the PGA. Like most PGAs, there is a common-mode range restriction due to the fact that amplifier outputs are not able to swing completely to either supply rail. In the case of the ADS1262, the PGA outputs will saturate once they are within 300 mV from AVDD or AVSS.

    To avoid this issue, it is important to bias your sensor's output voltage(s) to the PGA's input common-mode range. Then you can measure a 0V differential signal, for example, if both V_INP and V_INN are at 2.5V.

    Alternatively, it may be easier in some applications to power the ADS1262 with a bipolar analog supply (for example, AVDD = 2.5V, and AVSS = -2.5V). Powering the PGA with a bipolar supply makes 0V the mid-supply voltage and doesn't violate the PGA's common-mode range when an input is connected to 0V.

  • 0 in reply to Christopher Hall
    Prodigy 60 points

    hello Sir,

    Thank you for this information

    I have read datasheet of ADS1262.

    Is there any circuit i have applied for Level Shift voltage?

    Please suggest regarding thisand also there is pin VCom ,How to used this pin?

    I also want to have 80 sps and want to 20 bits stable,

    Would  suggest any circuit regarding to have  stable 20 bits ?

    It will be very grateful for me.

  • 0 in reply to Pranav Kumar MOudgil
    TI__Mastermind 44640 points

    Hi Pranav,

    Would it be possible for you to share the details (part # or datasheet) for the sensor you are using?
    At the moment I'm not sure what kind of circuit to recommend as I'm not used to seeing hall sensors used with the ADS1262.

    For general circuit recommendations, I would take a look at this circuits eBook (here: http://www.ti.com/lit/slyy137).

    If it is possible to change the common-mode output voltage of your sensor by some other means, then I would do that and avoid having to add any additional external circuitry. Adding amplifiers to the front-end of the ADS1262 usually has the effect of adding additional noise to the signal and degrading the overall system resolution.