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ADC124S101: Settling time issue

Part Number: ADC124S101

Hi,

In relation to the previous question, I am experiencing a similar problem due to the RC time constant being too big and my internal sampling capacitor not discharging quickly enough, hence affecting the value of my subsequent measurement.

I was wondering if there is a similar 4-channel ADC in TI's ADC family that mitigates this issue with a smaller value of the internal sampling capacitor. Due to board size constraints, I do not think I have the luxury of putting an input buffer for each of the 4 channels I am using. 

Other suggestions on improving the performance also welcome.

Regards
Ben

  • Hello,

    Without seeing the schematic we can't offer a possibly quick fix, but I will provide a great informative video that covers the topic of driving SAR converters without Amplifiers in great detail.  It explains all the tradeoffs and error estimates.  I've copied the link and abstract below for reference:

    https://training.ti.com/ti-precision-labs-driving-sar-without-amplifiers

    This video shows how to select the resistor and capacitor for good settling on SAR ADC without amplifiers.   Some common examples of SAR ADC usage without amplifiers are monitoring power supplies or monitoring a slow moving sensor such as a thermistor.  In previous videos we learned how to select the amplifier and external RC filter to achieve good settling.  In these videos we used simulation and a parametric search to find the optimal RC value.  Although this method can be used on circuits without amplifiers, it is much easier to use some simple equations to select the values.  The reason the simple equations can be used here but not for circuits using amplifier drive is that circuits without amplifiers are simple first order circuits and amplifier circuits are higher order more complex systems.  The higher order systems are difficult to model mathematically as they depend on many factors such as gain and output load.  The first order system on the other hand has a simple mathematical solution that yields a set of equations that can be used to find the RC filter and sampling rate needed for proper settling.