TL431BCDBVRG4 — precision shunt reference, now obsolete
The Texas Instruments TL431BCDBVRG4 is an adjustable shunt voltage reference in a SOT-23-5 package, delivering a 2.495 V fixed minimum output with a ±0.5% tolerance. The part is officially marked obsolete by Texas Instruments. Any stock on the market is new-old-stock or surplus, sourced through independent distribution.
The 2.495 V reference is the starting point for any adjustable shunt-regulator design — the feedback divider sets the output anywhere from that floor up to 36 V. The ±0.5% tolerance (B grade) is the key spec for precision supplies, error amplifiers, or secondary-side regulation in a flyback converter where the reference accuracy sets the output-voltage tolerance. Cathode current range is 600 µA minimum to 100 mA maximum. The 600 µA floor dictates the bias resistor value in a shunt regulator — go below it and the device stops regulating. The 100 mA ceiling limits how much load the reference can sink directly; for higher currents you need a series-pass transistor. Not rated for automotive or extended industrial environments where the ambient exceeds 70°C.
Sourcing an obsolete part — what to expect
The remaining inventory is held by independent distributors and surplus houses. Pricing and availability vary with market conditions and are confirmed only at quote time against a specific BOM quantity. The closest pin-compatible alternative in the same family is the TL431BCDBVR (the non-G4 suffix variant), which shares the same SOT-23-5 footprint and electrical specs — but that part may also face lifecycle pressure. For new designs, consider the TL431BQDBZR (AEC-Q100 qualified) or the TL431AIDBZR (industrial temp, -40°C to 125°C) as functional replacements, though verify the pinout and stability compensation.