±0.5% precision shunt reference in 8-SOIC
It delivers a ±0.5% initial tolerance — the 'B' grade — making it a step up from the standard 1% or 2% TL431 variants for applications that need tighter regulation without moving to a dedicated series reference. The output is adjustable from 2.495 V up to 36 V via two external resistors, with a 100 mA sink capability and a minimum cathode current of 700 µA for regulation.
The 100 mA output current is the maximum the shunt can sink while maintaining regulation. In a typical feedback application — say, an isolated flyback supply — the TL431 draws a few milliamps through the optocoupler LED, so the 100 mA ceiling leaves ample headroom for transient loads or parallel regulation paths. The ±0.5% tolerance at 25°C sets the initial accuracy floor. For a 5 V rail referenced through a resistor divider, a 0.5% reference contributes roughly half the error budget of a 1% part, which can eliminate a trim pot in production. The 700 µA minimum cathode current is the lowest current that keeps the device in regulation. Below that, the output voltage may drift. Design the bias resistor to guarantee at least 700 µA through the cathode over the full input voltage range.
Sourcing this BOM line
For dual-sourcing flexibility, the TL431 family includes multiple tolerance grades and package options. The TL431BIDRG4's ±0.5% grade is a direct fit for designs that previously used the 1% TL431AIDRG4, with no circuit change needed — just a tighter spec on the BOM.