It is a member of the LM336 family, designed as a low-cost, stable reference for A/D converters, D/A converters, and power-supply monitoring in commercial-temperature equipment. The shunt architecture means it behaves like a Zener diode — it regulates by sinking current through the cathode, which simplifies biasing in split-supply or single-supply rails.
Package and rework — 8-SOIC is a friendly footprint
The 1.27 mm pin pitch gives good clearance for inspection and touch-up under a hot-air station.
Output current and cathode bias — the practical limits
The LM336BDR-2-5 can source up to 10 mA from the output pin, which is enough to bias a single ADC reference input or a comparator threshold divider. The minimum cathode current is 400 µA — the bias resistor from the supply rail to the cathode must be sized to keep at least this much current flowing at all times, otherwise the reference drops out of regulation. For a 5V rail, a 6.2 kΩ resistor sets the bias current near 400 µA; a lower value increases headroom for load transients.