Answer: The TL431CDBZR is TI’s 2 % (C-grade) TL431 in a 3-pin SOT-23 (DBZ), on 3000-piece reels. Vref is 2440 / 2495 / 2550 mV at 25 °C, it needs ≥ 1 mA of cathode current to regulate, the cathode may go up to 36 V, and it is rated for 0–70 °C. Pinout: 1 = cathode, 2 = REF, 3 = anode. Marking: T3C3, T3CG, T3CS or T3CU. (TI SLVS543S, pp.4–6 and Addendum p.41.)
Key specifications
| Parameter | Value | Condition | Source |
|---|---|---|---|
| Reference voltage Vref (min / typ / max) | 2440 / 2495 / 2550 mV (±2 %) | VKA = Vref, IKA = 10 mA, TA = 25 °C | §6.5 p.6 |
| Vref deviation over 0–70 °C, VI(dev) | 6 typ / 16 max mV | SOT-23-3 and TL432 devices; max − min over the rated range | §6.5 p.6, note 1 |
| ΔVref / ΔVKA | −1.4 typ / −2.7 max mV/V (ΔVKA = 10 V − Vref); −1 / −2 mV/V (36 V − 10 V) | IKA = 10 mA | §6.5 p.6 |
| Reference input current Iref | 2 typ / 4 max µA | IKA = 10 mA, R1 = 10 kΩ, R2 = ∞ | §6.5 p.6 |
| Iref deviation over temperature, II(dev) | 0.4 typ / 1.2 max µA | IKA = 10 mA, R1 = 10 kΩ, R2 = ∞ | §6.5 p.6 |
| Minimum cathode current for regulation Imin | 0.4 typ / 1 max mA | VKA = Vref | §6.5 p.6 |
| Off-state cathode current Ioff | 0.1 typ / 1 max µA | VKA = 36 V, Vref = 0 | §6.5 p.6 |
| Dynamic impedance | ZKA | 0.2 typ / 0.5 max Ω | |
| Cathode voltage VKA (recommended) | Vref to 36 V | Absolute maximum 37 V | §6.4 p.5; §6.1 p.5 |
| Cathode current IKA (recommended) | 1 – 100 mA | Absolute maximum −100 to 150 mA | §6.4 p.5; §6.1 p.5 |
| Operating free-air temperature (C grade) | 0 – 70 °C | TL43xxC; junction absolute maximum 150 °C | §6.4 p.5; §6.1 p.5 |
| RθJA / RθJC(top), DBZ (SOT-23-3) | 206 / 76 °C/W | JEDEC metrics, SPRA953 | §6.3 p.5 |
| Orderable / packing | TL431CDBZR: Active, SOT-23 (DBZ) 3-pin, 3000 / large T&R, MSL 1 260 °C | Device marking T3C3, T3CG, T3CS, T3CU | Package Option Addendum, PDF p.41 |
Pinout (SOT-23-3, DBZ)
| Pin (DBZ, SOT-23-3) | TL431 | TL432 (for comparison) |
|---|---|---|
| 1 | CATHODE | REF |
| 2 | REF | CATHODE |
| 3 | ANODE | ANODE |
Source: Table 5-1 and the DBZ top views, p.4. Anode is the common pin, normally tied to ground.
Other makers sell “TL431” in SOT-23 with either pin order, K/R/A or R/K/A, so check the pinout against the exact ordering code before you copy a footprint. The TI part with the same package but swapped pins 1 and 2 is the TL432ACDBZR.
Design notes
Setting the voltage. With a divider R1 (cathode to REF) and R2 (REF to anode), VKA = Vref × (1 + R1/R2) + Iref × R1 (Figure 7-2, p.19). The equation holds only while the cathode current is above Imin, so the part has enough loop gain (§9.2.2.2.1 p.26). Use the TL431 calculator to pick E24/E96 pairs and the series resistor.
Worked shunt example (12 V ±10 % in, 5 V out, 0–10 mA load). R1 = R2 = 10 kΩ gives 2.495 V × 2 + 2 µA × 10 kΩ = 5.010 V typical, and the divider draws 0.25 mA. The series resistor must still deliver 1 mA into the cathode at 10.8 V and full load. Using TI’s “>1 mA (Imin(max))” figure (§8.1 p.21): Rs ≤ (10.8 − 5.01) / (10 + 1 + 0.25 mA) = 515 Ω, so choose 510 Ω. At 13.2 V and no load, Rs passes 16.1 mA, of which 15.8 mA flows into the TL431CDBZR: P = 5.01 V × 15.8 mA ≈ 79 mW, a rise of about 16 °C with RθJA = 206 °C/W. Rs itself dissipates about 0.13 W, so size its power rating for that, not for the 79 mW in the TL431.
What the grade does not cover. The tolerance printed on the grade is Vref at 25 °C with VKA = Vref. TI lists the other error terms separately (§9.2.2.2.2 p.27): resistor tolerance, VI(dev) over temperature, ΔVref/ΔVKA, and |ZKA| × ΔIKA. At a 5 V output each term is scaled by (1 + R1/R2) = 2:
- VI(dev) of 16 mV max becomes up to 32 mV at the output over 0–70 °C (0.64 %).
- Raising VKA from 2.495 V to 5.01 V (ΔVKA = 2.5 V) moves Vref by −1.4 mV/V typ to −2.7 mV/V max, i.e. −3.5 to −6.8 mV, or −7 to −13.5 mV at the output.
- A 10 mA swing in cathode current through |ZKA| = 0.5 Ω max adds 5 mV at VKA = Vref.
On a C-grade part the initial tolerance (2440–2550 mV, i.e. ±55 mV on Vref and ±110 mV at 5 V) dominates. If the error budget above is tight, the 1 % TL431ACDBZR cuts that term to ±25 mV (±50 mV at 5 V); the temperature and line terms stay the same.
Capacitors on the cathode. TI states the TL43xx is internally compensated and stable with no capacitor between cathode and anode (§8.3 p.22). If you add one, or if the load itself is capacitive, check the value against the stability boundary charts, Figure 6-16 (p.17) and Figure 6-18 (p.18). Some combinations of capacitance and cathode current fall outside the stable region, so “adding a bigger cap” is not automatically safer.
SOT-23 heat. RθJA is 206 °C/W for DBZ (§6.3 p.5). TI gives PD = (TJ(max) − TA) / RθJA and warns that running at the 150 °C absolute limit can affect reliability (§6.4 note 1, p.5). Even with 125 °C as your own design limit at TA = 70 °C, the budget is (125 − 70) / 206 ≈ 0.27 W, about 53 mA at VKA = 5 V, well below the 100 mA current rating.
Comparator use. Without feedback from cathode to REF, the TL431 runs open loop and switches as a comparator with a built-in 2.5 V threshold (§8.4.1 p.22). It still needs the minimum cathode current while on.
Pitfalls specific to TL431CDBZR
- Copying an SOT-23 footprint between makers. TI’s TL431 DBZ is K/R/A, its TL432 is R/K/A, and other makers ship both orders under “TL431” names. Check the pinout against the ordering code (p.4).
- Starving the cathode. Imin is 0.4 mA typical but 1 mA max for the C grade (p.6). Size the series resistor at minimum input and maximum load.
- Large divider resistors. Iref is up to 4 µA (p.6). With R1 = 100 kΩ, that alone moves the output by up to 0.4 V.
- Using it below 0 °C. The C grade is specified for 0–70 °C only (§6.4 p.5). TI’s I and Q grades cover −40 to 85 °C and −40 to 125 °C.
- Reading T3C marking as “TL431” only. T3C identifies the 2 % TI TL431 in DBZ. The 1 % TL431A is TAC, and TL432A is T4B (Addendum pp.34, 41, 44). See the TL431 SOT-23 marking codes.
Part numbers (information only)
| Ordering code | Status | Packing | Marking | Source |
|---|---|---|---|---|
| TL431CDBZR | Active | 3000, large T&R | T3C3, T3CG, T3CS, T3CU | Addendum p.41 |
| TL431CDBZT | Active | 250, small T&R | T3CG, T3CS, T3CU | Addendum p.41 |
The addendum also lists G4 and ”.A” variants of both. Marking options vary by assembly site, so one reel can carry a different suffix letter from the last.
FAQ
- What is the TL431CDBZR marking code? T3C3, T3CG, T3CS or T3CU, per TI’s Package Option Addendum (p.41). All four mean the same 2 % TL431 in SOT-23.
- What is the TL431CDBZR pinout? Pin 1 cathode, pin 2 REF, pin 3 anode (TI SLVS543S p.4). The TL432 swaps pins 1 and 2.
- What is the minimum current for a TL431CDBZR? 1 mA maximum Imin for the C grade. Design for at least 1 mA at the worst-case input and load.
- What is the difference between TL431CDBZR and TL431ACDBZR? Initial accuracy: ±2 % (2440–2550 mV) versus ±1 % (2470–2520 mV). The A grade also has a tighter Imin max (0.6 mA) and Ioff max (0.5 µA).
- Does the TL431CDBZR need an output capacitor? No. TI says it is stable with no capacitor. If you add one, check it against the stability charts on pp.17–18.
Related (internal links)
- TL431 calculator
- TL431 SOT-23 marking codes
- TI TL431ACDBZR (1 % grade)
- TI TL432ACDBZR (R/K/A pinout)
- TL431CDBZR alternatives
Sources (retrieved 2026-10-26)
- Texas Instruments, TL431, TL432 Precision Programmable Reference, SLVS543S (revised May 2024), including the Package Option Addendum: https://www.ti.com/lit/ds/symlink/tl431.pdf
Disclaimer
Values are copied from TI SLVS543S (revised May 2024) and its Package Option Addendum, read on 26 Oct 2026. Ordering data and markings can change; check the current TI addendum before you release a BOM, and validate the circuit on your own hardware.
Reviewed by: Jasper · Updated: 2026-10-26