In this section we gain a basic understanding of a custom SAR ADC reference input SPICE model based on datasheet parameters.  This particular model is called the “Discrete Charge model” and is based on the switching capacitive load of the SAR ADC at the reference input.  The SPICE model can be used to verify the settling performance on the voltage reference input so that we can be confidant that ADC performance is not limited by the reference design.