TL431BFDT-QR
Adjustable Precision Shunt Regulator – Quick Reference & Datasheet Extract
(Nexperia, Rev. 2 – 30 Apr 2024)

1. Device Identification1.1 Type number: TL431BFDT-QR1.2 Package: SOT23 (3-lead plastic surface-mounted)1.3 Pinning (mirrored): 1 – REF (reference) 2 – K (cathode) 3 – A (anode)1.4 Automotive qualified: AEC-Q100 Grade 11.5 RoHS / Pb-free: Yes1.6 Moisture sensitivity: MSL-1
2. Grade & Accuracy2.1 Grade: “B” – 0.5 % tolerance on Vref2.2 Reference voltage range (Vref): 2.483 V … 2.507 V (TA = 25 °C, IK = 10 mA)
3. Key Electrical Characteristics (25 °C unless noted)3.1 Vref (typ): 2.495 V3.2 Cathode-anode voltage (VKA): 2.495 V … 36 V (operating)3.3 Cathode current (IK): 1 mA … 100 mA (continuous)3.4 Minimum cathode current for regulation: 0.6 mA max3.5 Off-state current (Ioff): 0.5 µA max (VKA = 36 V, VREF = 0)3.6 Reference input current (Iref): 4 µA max (IK = 10 mA, R1 = 10 kΩ)3.7 Dynamic impedance (ZKA): 0.5 Ω max (f < 1 kHz, IK = 0.1 … 100 mA)3.8 Temperature drift of Vref: 9 mV typ (0 °C … 70 °C), 34 mV max (-40 °C … 125 °C)
4. Absolute Maximum Ratings4.1 VKA: 37 V4.2 IK: –100 mA … +150 mA4.3 Iref: –0.05 mA … +10 mA4.4 Total power dissipation (Ptot): 350 mW (FR4, standard footprint, TA ≤ 25 °C) 580 mW (FR4, 1 cm² Cu anode pad) 950 mW (ceramic PCB, Al₂O₃)4.5 Junction temperature (Tj): 150 °C4.6 Storage temperature (Tstg): –65 °C … +150 °C4.7 ESD HBM: 4 kV
5. Thermal Data5.1 Rth(j-a) (SOT23, typical): 360 K/W (free air) 216 K/W (FR4, 1 cm² Cu) 132 K/W (ceramic PCB)5.2 Rth(j-sp): 50 K/W (solder-point)
6. Temperature Ranges by Variant Letter6.1 “B” grade devices are offered in three temperature variants: TL431BCDBZR-Q: 0 °C … +70 °C TL431BIDBZR-Q: –40 °C … +85 °C TL431BQDBZR-Q: –40 °C … +125 °C TL431BFDT-Q / TL431BMFDT-Q: –40 °C … +125 °C (same die, mirrored pinning)
7. Functional DescriptionThe TL431BFDT-QR is a 3-terminal adjustable shunt regulator.An internal band-gap reference (2.495 V typ) is compared with an external resistor-divider between cathode and reference pin; the device sinks current to hold VKA at the programmed value.It replaces discrete Zeners in precision voltage references, error amplifiers, SMPS isolated feedback, over-voltage monitors, current-limit circuits, etc.
8. Typical Applications (formulas use Vref = 2.495 V)8.1 Shunt regulator: VOUT = Vref·(1 + R1/R2)8.2 Series-pass regulator: VOUT = Vref·(1 + R1/R2) (add external PNP/NPN)8.3 Single-supply comparator: Vth = Vref (temperature-compensated)8.4 Precision current sink: ISINK = Vref / RS8.5 High-current shunt: add external pass transistor8.6 SMPS opto-isolated feedback: TL431 in 2-pole compensation network (see Fig. 26 datasheet)
9. Stability & Compensation9.1 Stable without capacitor for VKA ≥ 5 V, IK ≥ 1 mA9.2 For inductive or capacitive loads add 100 pF … 1 nF across VKA or a 150 Ω series resistor9.3 Phase margin graphs: see Fig. 13 (gain vs. freq.) & Fig. 15 (ZKA vs. freq.)
10. Marking & Ordering10.1 Marking code (topside): “AT%” (% = manuf. site code)10.2 Reel diameter: 180 mm (7″)10.3 Pieces/reel: 3 00010.4 Lead finish: matte Sn (100 %)
11. Package Outline (SOT23)11.1 Body: 2.9 mm × 1.3 mm × 1.0 mm11.2 Lead pitch: 0.95 mm11.3 Footprint & stencil: see Figs. 28–29 (reflow & wave)
12. Soldering Profile12.1 JEDEC J-STD-020C, Pb-free peak 260 °C12.2 MSL-1: unlimited floor life ≤ 30 °C / 85 % RH
13. Reliability & Qualification13.1 AEC-Q100 Grade 1 qualified (–40 °C … +125 °C ambient)13.2 HTOL, HAST, uHAST, TC, PTC, ESD, latch-up, solder heat, etc. – full automotive matrix
14. Revision HistoryRev. 2 – 30 Apr 2024: updated application diagrams & legend (Fig. 22 & 26)Rev. 1 – 12 May 2023: initial release
15. Legal & DisclaimerThis extract is for quick reference only.Always consult the latest official datasheet before design-in.Nexperia products are sold subject to their standard terms & conditions of commercial sale.