I just wanted to construct a simple constant-current source using a shunt regulator. The shunt regulator TS431 – which I had lying around – is made by both ST and by Taiwan Semiconductor.
Both manufacturers use the same component name, the same package and the same description. However, there is one significant difference: while the ST part has an internal reference voltage of 1.2 V (possibly derived from a bandgap reference) the Taiwanese counterpart has an internal reference voltage of 2.5 V (possibly derived from a Zener junction).
Why is this important? Look at the schematic of a constant-current source below:
The current through the load, IL, is determined by the ratio IL=Vref/RCL. Having different reference voltages gives you significantly different currents. And the same is true for every other possible circuit using this component.
This is the first time that I see the same component made by different manufacturers with such different characteristics. And this is not even the question of counterfeit components, these are two official manufacturers!