This document describes the errors that may occur when using an adjustable shunt voltage reference like TL431 in programmable mode and provides a method to calculate the relative error. The document also discusses the impact of inner precision and resistor precision on the overall circuit.
This document provides a method to determine the relative error on the output voltage when an adjustable shunt voltage reference, such as the TL431, is used in programmable mode. It addresses errors arising from the programming process, specifically the inner precision of the voltage reference and the precision of external resistors used in the bridge configuration.
The note presents a schematic for programming the voltage reference and derives a final formula to calculate the total relative error. This formula accounts for variations in the reference voltage and the resistor values (R1 and R2) to help users estimate the accuracy of their specific circuit design.
| Product Type | Adjustable shunt voltage reference |
|---|---|
| Example Precision (TL431A) | +1% |
The relative error is calculated using a final expression derived from the partial derivatives of the output voltage with respect to the reference voltage and the resistor values.
The calculated 5V output precision is 4.3%.