Designing a reliable circuit that employs a voltage reference requires a more detailed look at device parameters than most data sheets provide.
The key to optimizing the performance of any circuit begins with determination of the major performance criteria or “figures of merit” (“FOM”). Without a clear understanding of these key device parameters, circuit performance could be compromised. Figure of merit can vary depending on the circuit and application. Most engineers would likely consider the figures of merit (FOM) for a precision voltage reference to be:
DC initial accuracy
Temperature coefficient
Thermal hysteresis
Output noise
Reverse current or headroom
Output impedance
While these are arguably key characteristics, they may not be the most important and the performance in your circuit may often fall far short from the datasheet specifications.
A prerequisite to defining the mathematics of the reference is the understanding that there are different types of references. Specifically, there are series references and shunt references, as well as some that can be operated as either series or shunt devices. References are also either based on bandgap or buried zener elements.