Voltage references – precision devices that maintain a constant output voltage over time despite fluctuations in supply voltage and temperature –- are not new. They have long been used as key building blocks in data conversion and signal conditioning. But as their application spaces expand, understanding their specifications and how they contribute to error is necessary for selecting the right reference for the situation. While they are simple parts, which often may have only two or three pins, there are numerous parameters that affect performance.
The first thing to understand is that there are two types of voltage reference topologies: shunt and series. Each has its own set of strengths and use cases.
A shunt reference is functionally similar to a Zener diode, where the voltage drop across the device is constant after the device reaches a minimum operating current. The shunt reference regulates the load by acting as a constant voltage drop and shunting excess current not required by the load through the device to ground. An external resistor sets the total supply current and acts as the voltage drop between the input supply and the reference voltage
A series reference does not require an external resistor and only consumes as much current as required by the load, plus a small quiescent current. However, since the input voltage passes directly into the reference device instead of through a series resistor, a series reference has a maximum-rated input voltage that you must account for.
There’s a lot more to explore in the document, “Tips and tricks for designing with voltage references,” which provides a comprehensive overview of voltage reference basics and application design.