7 Voltage References and Ranges

The references shown in these examples are simple. They are for ratiometric applications where the ADC range is the rail. The references shown are V_CC/2, or at the mid-scale of the ADC range. This proportion is required for these circuits. 3.3V or 5V can be used in any of these designs; the references would be 1.65V or 2.5V, respectively. These designs will work with absolute references as well, as long as the V_REF is one-half of the ADC full-scale range.

The other requirement is a good buffer driving the reference signal. These designs put a wide range of loads on the reference, and a buffer is essential. For in-depth information on buffering references for precision and high-resolution designs, see Application Note Voltage Reference Filters (SBVA002).