Adjustable shunt reference with ±0.5% precision
The TL431BQLPRE3 is a three-terminal adjustable shunt regulator from the TL431 family, offering a ±0.5% initial tolerance on the 2.495 V internal reference. It sinks up to 100 mA cathode current and regulates from Vref up to 36 V with a single external resistor divider. The TO-92-3 through-hole package (formed leads per TO-226AA) is a workbench staple — easy to hand-solder, easy to probe, and it survives multiple rework cycles without lifting a pad. The formed lead bend means the part sits flush on the board; just confirm the lead spacing matches your existing TO-92 footprint before committing.
The ±0.5% tolerance is tight enough for most 8- to 12-bit ADC reference or feedback divider applications — you get consistent regulation across temperature without trimming. The 100 mA cathode current ceiling handles optocoupler bias, LED drivers, or power-supply feedback loops without needing a buffer transistor. Minimum cathode current is 700 µA, which sets the bias resistor value for the shunt. At light loads, keep the bias current above that floor to maintain regulation — a 1 kΩ resistor from a 5 V rail gives 4.3 mA, well clear of the minimum.