Shunt reference in SC-70-6 — the ±1 % tolerance tier
It delivers a ±1 % initial tolerance on the 2.495 V internal reference, which is the precision grade within the TL431 family — the standard-grade parts carry a ±2 % or looser spec. For a power-supply feedback loop or an ADC reference that needs better than 2 % accuracy without an external trim, this is the tier to spec.
Output current and cathode current — the bias resistor decision
The device sinks up to 100 mA at the cathode, with a minimum cathode current of 700 µA to maintain regulation. That 700 µA floor sets the upper limit on the series resistor from the supply rail — size it so the current never drops below that threshold at the lowest input voltage and highest load. The 100 mA ceiling covers most local reference and error-amplifier loads; if your design needs more than 100 mA sink, step up to the TL431A with an external pass transistor.