TL431AIDBVRG4 - 2.495V Adjustable Shunt Reference | Texas Instruments
MPN: TL431AIDBVRG4 ✓ Active| Qty | Unit Price | Extended |
|---|---|---|
| 1 | $0.45 | $0.45 |
| 10 | $0.38 | $3.80 |
| 100 | $0.24 | $24.00 |
| 500 | $0.18 | $90.00 |
| 1,000 | $0.14 | $140.00 |
| 3,000 | $0.12 | $360.00 |
TL431AIDBVRG4 Overview
A shunt voltage reference is a two-terminal (or three-terminal with adjustment) device that maintains a constant voltage across its terminals by sinking varying amounts of current through a parallel load. Shunt references sit at the same hierarchy level as series (bandgap) references, but are wired in parallel with the load rather than in series — making them functionally closer to a Zener diode than to a LDO regulator. The TL431 family implements an adjustable bandgap core with an on-chip op-amp and reference network, allowing the user to set the output via an external resistor divider.
Key features include a typical output impedance of 0.2 Ω at low frequencies, a low output noise of approximately 0.2 µV_RMS across the audio band, and a temperature coefficient of 109 ppm/°C (max). The device sinks from 1 mA (minimum cathode current for regulation) up to 100 mA continuously, with absolute-maximum cathode voltage of 37 V. The SOT-23-5 footprint offers a compact land pattern of approximately 2.9 mm × 1.6 mm, suiting it to high-density switching supply and isolated feedback designs.
The TL431 architecture pairs a precision bandgap reference with a transconductance error amplifier driving an open-collector pass transistor. When the divided output drops below the internal 2.495 V bandgap, the amplifier reduces cathode conduction, raising V_OUT; when it rises above, conduction increases, clamping V_OUT. This feedback loop yields tight line and load regulation in closed-loop SMPS optocoupler and primary-side feedback circuits.
Typical applications include isolated DC-DC converter secondary-side regulation, switch-mode power supply (SMPS) feedback loops, adjustable Zener replacement, voltage monitoring, and precision comparator thresholds. Its wide cathode voltage range makes it ideal for 3.3 V, 5 V, 12 V, and 24 V rails. The combination of small SOT-23 footprint and high accuracy is particularly valuable in industrial PSU designs with tight PCB constraints.
When designing with this part, ensure the cathode current stays between 1 mA and 100 mA under all load and line conditions. Add a 0.1 µF bypass capacitor close to the cathode pin when the device operates in fast-loop SMPS feedback paths to suppress transient oscillation. Choose resistors in the divider for low standby current, and ensure the divider current is at least 100× the TL431 reference bias current for accuracy.
This page synthesizes distributor pricing, drop-in alternatives, and practical design notes not found in the manufacturer datasheet.
Drop-in alternatives for TL431AIDBVRG4 — same package, pin-to-pin compatible. Different-package parts requiring PCB rework are excluded.
Variants in this series
Same-series models that are drop-in compatible with TL431AIDBVRG4 (same form factor and footprint) — differing in Operating Temperature Range, Package.
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TL431AIDBVRG4 Specifications
| Reference Type | Adjustable Shunt Voltage Reference |
| Output Voltage (Vref) | 2.495 V (adjustable up to 36 V) |
| Initial Accuracy (A Grade) | ±1 % |
| Cathode Voltage Range | 2.495 V to 36 V |
| Maximum Cathode Current (I_KA) | 100 mA |
| Minimum Cathode Current for Regulation | 1 mA (typical) |
| Typical Output Impedance | 0.2 Ω |
| Typical Output Noise | 0.2 µV_RMS |
| Temperature Coefficient (max) | 109 ppm/°C |
| Operating Temperature Range | -40 °C to +85 °C |
| Package | SOT-23-5 (DBV), 5-pin |
| Mounting Type | Surface Mount |
| MSL Level | 1 (unlimited floor life) |
| RoHS / Lead-Free | Compliant / Lead-free (G4 suffix) |
TL431AIDBVRG4 Pin Configuration
| Pin 1 | REF — Reference input (feedback, sets V_OUT via external divider) |
| Pin 2 | ANODE — Anode (ground reference for the shunt regulator) |
| Pin 3 | NC — Not connected (no internal bond) |
| Pin 4 | NC — Not connected (no internal bond) |
| Pin 5 | CATHODE — Cathode (V_OUT, sinks current to regulate) |
Typical Applications
TL431AIDBVRG4 is suitable for 6 applications: Isolated DC-DC Converter Secondary-Side Regulation, Switch-Mode Power Supply (SMPS) Feedback Loop, Adjustable Zener Diode Replacement, Voltage Monitoring and Power-Good Circuit, Precision Comparator Threshold Reference, Industrial 24 V Bus Sensor Power Conditioning.
Isolated DC-DC Converter Secondary-Side Regulation
The TL431AIDBVRG4 serves as the precision reference and error amplifier on the secondary side of an isolated DC-DC converter, paired with an optocoupler to close the feedback loop across the isolation barrier. With Vref = 2.495 V and ±1% initial accuracy, it enables tight output regulation on 3.3 V, 5 V, 12 V, or 24 V rails. The 100 mA cathode current capability directly drives the optocoupler LED without an additional buffer transistor. Low output noise of 0.2 µV_RMS keeps the feedback path quiet, minimizing output ripple. Typical use: between the output filter capacitor and the TL431's cathode–anode pair, with the divider setting V_OUT to the desired rail.
Recommended
Switch-Mode Power Supply (SMPS) Feedback Loop
In offline flyback, forward, or buck SMPS designs, the TL431AIDBVRG4 provides the secondary-side error amplification, comparing the divided output against its 2.495 V bandgap and modulating the optocoupler LED current. The SOT-23-5 footprint keeps the secondary-side PCB compact, fitting inside phone chargers, adapter bricks, and 1–100 W industrial PSU modules. Its 109 ppm/°C temperature coefficient is acceptable for ±5% output regulation across commercial -40 °C to +85 °C ambient range. The minimum 1 mA cathode current guarantees regulation even at light no-load standby conditions.
Recommended
Adjustable Zener Diode Replacement
The TL431AIDBVRG4 replaces conventional 2.4 V–36 V Zener diodes with a sharper knee, lower dynamic impedance (0.2 Ω typical vs Zener's 5–50 Ω), and programmable voltage via an external resistor divider. In voltage-clamping, level-shifting, and overvoltage protection circuits, this yields tighter clamping tolerances and dramatically lower noise. The SOT-23-5 package is far smaller than axial Zener diodes (DO-35/DO-41), saving PCB area. Engineers commonly use it in instrumentation input protection and analog signal-conditioning boards.
Recommended
Voltage Monitoring and Power-Good Circuit
A TL431AIDBVRG4 paired with a precision comparator or directly with a microcontroller ADC input creates a compact undervoltage/overvoltage monitor for 3.3 V, 5 V, or 12 V rails. The internal 2.495 V reference and ±1% accuracy give a well-defined threshold, while the cathode output can directly drive an MCU reset line or a power-good LED. The 100 mA sink capability eliminates the need for an extra transistor when driving optocouplers or small relays. Used in server PSUs, industrial PLCs, and battery management systems.
Recommended
Precision Comparator Threshold Reference
Using the TL431AIDBVRG4 as an external precision reference in front of a comparator IC yields tighter thresholds than the comparator's internal reference. For example, in a battery low-battery detection circuit, the 2.495 V reference sets a precise cutoff voltage that is stable across temperature (109 ppm/°C). The cathode pin can drive the comparator input through a divider, and the wide operating range (2.495 V–36 V) accommodates monitoring of multi-cell battery stacks up to 24 V. Low 0.2 µV_RMS output noise prevents false threshold crossings.
Industrial 24 V Bus Sensor Power Conditioning
In industrial 4-20 mA loop, PLC, and factory-automation sensor interfaces, the TL431AIDBVRG4 conditions the 24 V industrial bus down to a stable 5 V or 3.3 V reference for analog front-ends. Its 36 V maximum cathode rating comfortably tolerates 24 V nominal plus transient spikes, and the SOT-23-5 footprint allows dense multi-channel designs on small PCBs. The ±1% accuracy over -40 °C to +85 °C enables reliable threshold detection in noisy factory environments. Common in process control and instrumentation modules.
Recommended
Recommended Products Summary
Engineering reference data for TL431AIDBVRG4 — comparison, design guidance, and compliance information.
Selection Guide
Comparison with Alternatives
| Parameter | This Product | TL431BIDBVRG4 | TL431AIDBVR | TL431ACDBVR | TL431BCDBVR | KA431A | AZ431AN-AE1 |
|---|---|---|---|---|---|---|---|
| Package | SOT-23-5 (DBV) | SOT-23-5 (DBV) - same | SOT-23-5 (DBV) - same | SOT-23-5 (DBV) - same | SOT-23-5 (DBV) - same | SOT-23-5 (DBV) - same | SOT-23-5 (DBV) - same |
| Brand | Texas Instruments | Texas Instruments | Texas Instruments | Texas Instruments | Texas Instruments | onsemi | Diodes Incorporated |
| Reference Voltage (Vref) | 2.495 V | 2.495 V | 2.495 V | 2.495 V | 2.495 V | 2.495 V | 2.500 V |
| Initial Accuracy | ±1% (A-grade) | ±0.5% (B-grade) | ±1% (A-grade) | ±1% (A-grade, C-temp) | ±0.5% (B-grade, C-temp) | ±1% (A-grade) | ±1% (A-grade) |
| Maximum Cathode Current | 100 mA | 100 mA | 100 mA | 100 mA | 100 mA | 100 mA | 100 mA |
| Operating Temperature | -40 °C to +85 °C | -40 °C to +85 °C | -40 °C to +85 °C | -40 °C to +85 °C (C-temp) | -40 °C to +85 °C (C-temp) | -40 °C to +85 °C | -40 °C to +85 °C |
| RoHS / Lead-Free | Yes (G4 suffix) | Yes (G4 suffix) | Yes | Yes | Yes | Yes | Yes |
| Approx. Unit Price (qty 1) | $0.45 | ~$0.55 | ~$0.40 | ~$0.45 | ~$0.55 | ~$0.30 | ~$0.30 |
Key Differentiators
- Industry-standard TL431 platform (vs LM431)
- Compact SOT-23-5 footprint with same electrical performance as larger packages (vs TL431AILP (TO-92))
- Lead-free G4 packaging for modern RoHS assembly (vs TL431AIDBV (non-G4))
Design Notes
Ensure the cathode current (I_KA) stays between 1 mA and 100 mA under all operating conditions. At light loads, add a minimum-load bleed resistor (typically 10 kΩ across the output rail) to keep the TL431 in regulation. At heavy loads, calculate worst-case power dissipation: P_D = (V_IN − V_OUT) × I_KA + V_OUT × I_LOAD. For example, at V_IN = 24 V, V_OUT = 5 V, and I_LOAD = 50 mA through the cathode, P_D ≈ 0.95 W — derate against the SOT-23-5 thermal resistance (θ_JA ≈ 206 °C/W). Estimated junction temperature rise at 0.95 W is ~196 °C above ambient; the part MUST have adequate copper pour.
Place a 0.1 µF ceramic bypass capacitor directly across the cathode-to-anode pins (within 3 mm) when the TL431 is used in fast-loop SMPS feedback. This suppresses high-frequency oscillation that can occur in optocoupler-based feedback paths due to the optocoupler's parasitic capacitance combined with the TL431's transconductance. Also keep the feedback divider resistors (R1, R2) close to the REF pin to minimize noise pickup on the high-impedance reference node.
Do NOT use a divider current less than ~100× the TL431's REF pin bias current (typ. 4 µA). For a 5 V output, this means the divider current should be at least 0.4 mA, suggesting R1+R2 ≤ 12.5 kΩ. Below this threshold, REF bias current drift across temperature degrades output accuracy. Also avoid leaving the REF pin floating — always tie it to the divider midpoint. Finally, never reverse-bias the cathode-anode beyond the absolute-maximum rating of 37 V, even during transient events; add a TVS or clamp if inductive kickback is possible.
Route the REF pin trace away from switching node traces (e.g., the primary-side MOSFET drain or the optocoupler primary) to avoid coupling noise into the high-impedance feedback input. Use a ground plane under the TL431 to provide a low-impedance return for the cathode current. If designing for 6 kV+ surge immunity on industrial PSUs, leave a creepage gap of at least 6 mm between the primary-side optocoupler trace and the secondary-side TL431 trace.
Compliance Information
G4 suffix confirms lead-free RoHS-compliant terminal finish per TI documentation. Halogen-free per TI Material Declaration Standard. Not AEC-Q100 qualified; for automotive, choose TL431AQDBZRQ1 (AEC-Q100) instead.
