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ADS131A04: some questions to confirm

Part Number: ADS131A04

Hello,

ADS131A04 is delta-sigma (ΔΣ) ADC, is the S/H circuit same with SAR ADC? How to design the buffer circuit, is the same with SAR  ADC? 

In addition, the datasheet  describes that ADS131A04 is simultaneous-sampling, but it doesn't have the description how to control the simultaneous sampling, does it mean it has been integrated the internal  the ADS131A04? 

Best regards

Kailyn 

  • Hello Kailyn,

    Here's a couple of examples you can refer to for the input stage:

    You already found figure 38 for the input impedance (resistance and capacitance) which is a good starting point for what you need to design. This is the equivalent of the sample and hold circuit for this Delta Sigma. The values for the resistance and capacitance are specs listed in the datasheet.

    I don't know what your sensor is, but you'll find that most of our documentation assumes that isolated (you can see the transformer or Rogowski coil in the applications section) or the voltage is stepped down (voltage divider in the application section) to the proper value. The examples I linked above are more general purpose and are probably closer to your real system. Like a SAR ADC, you still have the goal is to get a low impedance connection to the ADC inputs. Reminder material in context of inputs to SAR ADCs can be found here: https://training.ti.com/ti-precision-labs-adcs-introduction-sar-adc-front-end-component-selection 

    As for simultaneously sampling, there are 4 separate ADCs (or the A04, anyway) inside the device package that will use the same signal to capture whatever is on the inputs. So, you don't control them individually, you just enable which channels you want to be simultaneously sampled (or turned off) using the CLOCK register (0x03[11:8]). 

    Best,

    -Cole

  • Hi Cole,

    Thank you for your detailed explanation.

    Best regards

    Kailyn