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ADS130E08: Analog input specefication

Vineeth N
Expert 1180 points
Part Number: ADS130E08
Other Parts Discussed in Thread: ADS131A04

Hi Team,

I want measure the current values from power line for my project. I need to have a sampling rate of maximum 5ksps and simultaneous sampling of 3 channels , So I choose ADS130E08 for my application. But while reading the data sheet of the same I find it is hard for me to understand the concept of differential input. Could you please give me an explanation on this. If I want measure a current in the range 0-30A rms from mains how should I decide the CT and input voltage to Analog pins of this ADC. And what is the concept behind common mode voltage at input? if I am using a reference 2.4V internal and AVDD 3.3V and PGA gain 1 what will be the limits of my analog input. In datasheet it is shown FSDI 4.8V what it means? Do I need give DC bias  AC signal at ADC input?

Regards,

Vineeth  

  • +1
    TI__Guru 66706 points

    Hi Vineeth,

    Thank you for your post.

    Our TI Precision Labs - ADCs portal has some very comprehensive training videos on the topics you mentioned above. I believe section 4.1 will cover the differences between differential and common-mode voltage, which are applicable to both SAR and Delta-Sigma ADCs.

    The absolute voltage on each input pin is limited by the supplies (AVDD and AVSS), while the differential input voltage is limited by the ADC full-scale range (-VREF/Gain to +VREF/Gain). You will need to size the CT and shunt resistor value in order to keep the differential voltage within range. 

    If the low-side of the shunt is reference to ground, you could use bipolar analogy supplies (i.e. +/-2.5 V) such that the common-mode is near mid-supply of the ADC. This gives you the most headroom on either input pin.

    Another device you might consider is the ADS131A04, which has an integrated negative charge pump so that signals can pass below ground without a negative supply.

    Regards,

    Ryan

  • 0 in reply to Ryan Andrews
    Expert 1180 points

    Hi Ryan,

    Thank you for your response. I will check precision labs then. 

    Regards,

    Vineeth