Introduction
This calibration aid provides a fixed +5V DC output useful for checking accuracy of measurement equipment, the design is based around X60003 high precision voltage reference, in a SOT23 package.
A TL431 shunt regulator supplies power to the device, and provides additional power supply filtering.
I recommend that power is supplied from a 9V battery as batteries tend to have lower noise than AC/DC supplies, it is also recommended that the calibration be undertaken at 25deg C.
Specifications
Nominal voltage: 5.000V
Intial accuracy: +/-1mV
Temperature coefficient: 10ppm/degC
Photos
PCB top view
Orignal design had an error with the TL431 A & K pin being swapped this has been corrected on the files in the download section, with the TL431 now in line with the text rotated 90deg.