Understanding and Applying Voltage References

28 Oct 2020

Specifying the right reference and applying it correctly is a more difficult task than one might first surmise, considering that references are only 2- or 3-terminal devices. In this article, get an overview of voltage references, circuit design, and key considerations for success in deployment.

As with many electronic components, the success and accuracy of voltage references are tied closely to the application in which they are used. The same reference might perform exceedingly poorly in one application while excelling in a different one. Therefore, it’s important to understand and account for variables like long-term stability, temperature fluctuations, reference accuracy, and voltage noise.

There are two styles of reference: shunt, functionally equivalent to a Zener diode; and series, not unlike a 3-terminal regulator. Series-mode references have the advantage that they draw only load and quiescent current from the input supply, whereas shunt references must be biased with a current that exceeds the sum of the maximum quiescent and maximum expected load currents. Since they are biased by a resistor, shunt references can operate on a very wide range of input voltages.

While references can be deceptively easy to use, there are a few common pitfalls to avoid. These include current-hungry loads, NC pins, board leakage, trim-induced temperature drift, burn-in, board stress, and temperature-induced noise. Be sure to click through to the article for complete and detailed explanations of these issues - plus get tips and tricks for how to avoid them.

When specifying a reference, keep in mind that initial accuracy, temperature coefficient, and long-term stability all play a role in the overall accuracy of the finished product. By taking some care in applying the reference, and by avoiding some key pitfalls, the reference’s inherent accuracy can be preserved.

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