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Project Notes

#454 VoltageReference/ADR4540

Exploring the ADR4540 precision reference, tested with an Arduino as an external voltage reference.



The Analog Devices ADR4540 is an “Ultralow Noise, High Accuracy Voltage Reference” with a 4.096V output voltage. Other parts in the series are available for reference voltages of 2.048, 2.5, 3.0, 3.3, and 5.0V.

Input and Output Stabilisation

The dataasheet recommends capacitors on the input to improve transient response and reduce noise:

  • 1 μF to 10 μF electrolytic or ceramic capacitor (transient response)
  • An additional 100nF ceramic capacitor (reduce supply noise)

An output capacitor is required for stability and to filter out low level voltage noise. For the ADR4540, the data sheet recommends minimum 100nF.

Test Circuit

In this example, the ADR4540 is used to provide a 4.096V reference for an Arduino (AREF). This requires the external reference to be enabled analogReference(EXTERNAL)

A voltage divider comprising a 10kΩ pot across the 5V supply provides a test input with a range of 0 to 5V. This test signal is read on the Ardunio A0 analog input.

Since AREF is enabled (analogReference(EXTERNAL)), analog readings are all with respect the the 4.096V reference voltage.

A Nokia 5110 display provides a realtime reading of the analog input and the derived voltage reading.


The ADR4540.ino sketch drives the demo.

It uses the Adafruit-PCD8544 Library to drive the 5110 display with hardware SPI.





Credits and References

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This page is a web-friendly rendering of my project notes shared in the LEAP GitHub repository.

LEAP is just my personal collection of projects. Two main themes have emerged in recent years, sometimes combined:

  • electronics - usually involving an Arduino or other microprocessor in one way or another. Some are full-blown projects, while many are trivial breadboard experiments, intended to learn and explore something interesting
  • scale modelling - I caught the bug after deciding to build a Harrier during covid to demonstrate an electronic jet engine simulation. Let the fun begin..
To be honest, I haven't quite figured out if these two interests belong in the same GitHub repo or not. But for now - they are all here!

Projects are often inspired by things found wild on the net, or ideas from the many great electronics and scale modelling podcasts and YouTube channels. Feel free to borrow liberally, and if you spot any issues do let me know (or send a PR!). See the individual projects for credits where due.