Three-terminal adjustable precision shunt regulator, a programmable Zener, in a SOT-23 package. A resistor divider from the cathode to REF sets the shunt voltage anywhere from the 2.5 V internal reference up to 36 V. It sinks 1-100 mA with ~0.2 ohm output impedance. The default feedback reference for switching supplies and adjustable linear regulators, and a precise Zener replacement. Wire REF to the divider tap, cathode to the node being regulated, anode to ground.

Pinout

Pin	Name	Type	Function
1	K	passive	Shunt cathode (K). Current-sink terminal referenced to ANODE; V(KA) may range from Vref (~2.5 V) up to the absolute-max 37 V. Continuous cathode current I(KA) = 1 mA to 100 mA in normal operation (abs-max −100 to 150 mA). Sinks current when V(REF-ANODE) exceeds Vref, regulating V(KA) at the value set by the external divider.
2	REF	input	Reference (feedback) input, threshold relative to ANODE. Internal error amp regulates V(REF) to Vref (~2.5 V nominal, 0.5%/1%/2% grades). Reference input current I(ref) is very small (abs-max −0.05 to 10 mA); typically driven from a resistor divider between CATHODE and ANODE to program V(KA) = Vref × (1 + R1/R2) + I(ref)·R1.
3	A	passive	Common return terminal (A), normally connected to circuit ground. All device voltages (V(KA), V(REF)) are referenced to ANODE. Carries the sum of cathode sink current and reference-input current.

Key specifications

Parameter	Value
Type	Adjustable shunt voltage reference
Reference voltage (Vref)	2.5 V (typ 2.495 V)
Output range	Vref to 36 V (external divider)
Cathode current	1 mA to 100 mA
Output impedance	0.2 Ω typ
Package	SOT-23 (DBZ)
Body (L×W×H)	2.9 × 1.3 × 1.1 mm

Ordering variants

Same part, different packaging or reel option.

TL431AIDBZR (SOT-23, ±0.5%)
TL431BIDBZR (SOT-23, ±0.5%, tighter tempco)

CAD (KiCad official)

Symbol: Reference_Voltage:TL431DBZ
Footprint: Package_TO_SOT_SMD:SOT-23
3D model: SOT-23 (KiCad packages3D)

Provenance

Data extracted from the manufacturer datasheet, not a distributor listing:

Datasheet: Texas Instruments datasheet (85 pp, sha256 49d4bc6e1bdcfab7, retrieved 2026-08-17, tier: manufacturer)
Extractor: ds2sf (Claude) — every pin and dimension is cited to a datasheet page; refuses to fabricate.
CAD: KiCad official libraries (CC-BY-SA 4.0).

Datasheet PDF