TL431AQDBZRQ1 - 36V Adjustable Shunt Voltage Reference | Texas Instruments
MPN: TL431AQDBZRQ1 ✓ Active| Qty | Unit Price | Extended |
|---|---|---|
| 1 | $0.42 | $0.42 |
| 10 | $0.34 | $3.40 |
| 100 | $0.22 | $22.00 |
| 500 | $0.16 | $80.00 |
| 1,000 | $0.12 | $120.00 |
| 3,000 | $0.09 | $270.00 |
TL431AQDBZRQ1 Overview
A shunt regulator or shunt voltage reference is a three-terminal device that maintains a fixed voltage across its terminals by sinking excess current. In the power-management hierarchy it sits alongside series references and LDO regulators as a voltage reference IC, but unlike a series regulator it is placed in parallel with the load and absorbs current through the cathode-anode path. The TL431 family, originally introduced as the industry-standard programmable reference, allows the output voltage to be set to any value between Vref (approximately 2.5V) and 36V using just two external resistors.
Key features include the A-grade 1% reference tolerance at 25C, specified thermal stability across the full automotive -40C to +125C range, low typical output impedance of 0.2 ohm, and low output noise in the 0.2 uV class over a narrow band. The internal precision bandgap reference and output comparator stage provide a sharp, fast response that makes the part usable both as a voltage reference and as an error amplifier in isolated feedback loops.
Technically, the TL431-Q1 behaves like a single-supply error amplifier with a 2.495V internal reference on one input and an open-collector output stage driving the cathode. When the REF pin voltage exceeds 2.495V, the device shunts current from cathode to anode, closing the regulation loop. This architecture is why the TL431 dominates optocoupler-based feedback in flyback and forward converters, where it compares a divided output voltage against the internal bandgap reference and modulates the optocoupler LED current.
Typical applications include secondary-side feedback regulation in automotive and industrial switch-mode power supplies, adjustable voltage supervision and threshold comparators, constant-current sources for LED biasing, and precision references for ADCs and battery chargers.
Design consideration: ensure the device always operates with at least 1 mA of cathode current to remain in regulation, and select the REF divider resistors low enough in value to keep the REF bias current error negligible.
This page synthesizes distributor data, AEC-Q100 lifecycle context, drop-in alternatives, and practical design guidance not consolidated in the manufacturer datasheet.
Drop-in alternatives for TL431AQDBZRQ1 — 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 TL431AQDBZRQ1 (same form factor and footprint) — differing in Adjustable Output Range, Operating Temperature Range, Package, Reference Voltage (Vref), RoHS Status.
Quick Comparison Tool — Select alternative parts for side-by-side comparison:
TL431BQDBZRQ1
✅ Drop-In📋 Reference alternative (not in catalog)
TL431LIQDBZRQ1
✅ Drop-In📋 Reference alternative (not in catalog)
TL431AQDBZR
✅ Drop-In✓ In Stock
$0.09 / Unit
View Datasheet →TL431ACDBVR
✅ Drop-In📋 Reference alternative (not in catalog)
KA431AZTA
✅ Drop-In📋 Reference alternative (not in catalog)
LM431ACM3
✅ Drop-In📋 Reference alternative (not in catalog)
AZ431ANTR-E1
✅ Drop-In📋 Reference alternative (not in catalog)
TL431AQDBZRQ1 Maximum Ratings & Electrical Characteristics
| Reference Voltage (Vref) | 2.495 V typical |
| Reference Voltage Tolerance | ±1% (A grade) at 25C |
| Adjustable Output Range | Vref (approx. 2.5 V) to 36 V |
| Maximum Cathode Voltage | 36 V |
| Maximum Cathode Current | 100 mA |
| Minimum Cathode Current for Regulation | 1 mA |
| Typical Output Impedance | 0.2 ohm |
| Temperature Drift | 82.59 ppm/C (typical) |
| Operating Temperature Range | -40C to +125C (automotive) |
| Qualification | AEC-Q100 (Q1 automotive) |
| Package | SOT-23 (DBZ), 3-pin |
| Mounting Type | Surface Mount |
| RoHS Status | Compliant (green package) |
| Output Type | Adjustable shunt |
| Function | Shunt voltage reference / error amplifier |
TL431AQDBZRQ1 Pin Configuration
| Pin 1 | REF — Reference input (internal 2.495V bandgap comparator input) |
| Pin 2 | ANODE — Anode terminal (lowest potential, typically ground) |
| Pin 3 | CATHODE — Cathode terminal (current sinks through device in regulation) |
Typical Applications
TL431AQDBZRQ1 is suitable for 6 applications: Automotive SMPS Secondary-Side Feedback, Adjustable Voltage Reference for ADCs, Precision Constant-Current Sources, Voltage Supervisor and Threshold Comparator, Industrial Power Supply Regulation, Battery Charger and Power-Bank Circuits.
Automotive SMPS Secondary-Side Feedback
The TL431AQDBZRQ1 is the de-facto standard error amplifier for optocoupler-based feedback in automotive flyback, forward, and buck converters. Its 2.495V precision bandgap reference with ±1% A-grade accuracy directly sets the output voltage regulation point through a simple two-resistor divider, while the open-cathode output modulates the optocoupler LED current to the primary controller. The AEC-Q100 qualification and specified thermal stability from -40C to +125C make it suitable under-hood and infotainment power supplies. Designers should guarantee a minimum of 1 mA cathode current for regulation and budget an RC compensation network from cathode to REF to stabilize the loop crossover, typically targeting 45-60 degrees of phase margin with a 10 kHz class bandwidth.
Recommended
Adjustable Voltage Reference for ADCs
With a 2.495V reference tolerance of ±1%, 82.59 ppm/C typical drift, and 0.2 ohm typical output impedance, the TL431AQDBZRQ1 provides an economical adjustable reference rail for microcontroller and SAR ADC power supervision or coarse references. Any output between approximately 2.5V and 36V is set with two resistors, letting one part serve multiple rails. In data-acquisition front-ends built around ADCs such as the AD7680 or AD7476 families, the TL431-Q1 can clamp, offset, or monitor supply rails before precision conversion. Note that for true high-precision conversion it should buffer through an op amp, since the shunt stage noise (0.2 uV class narrowband) and 1% initial accuracy exceed ADC INL error budgets in 16-bit systems.
Recommended
Precision Constant-Current Sources
Because the TL431AQDBZRQ1 holds its REF pin at a stable 2.495V when in regulation, inserting a sense resistor between anode and REF turns the device into a 2-terminal constant-current sink: I = 2.495V / Rsense. This configuration is widely used for LED bias strings, sensor excitation, and battery-charger current limiting in automotive modules. The A-grade 1% tolerance translates to roughly 1% current accuracy before resistor tolerance, and the -40C to +125C range keeps excitation stable across automotive environments. Keep cathode voltage headroom above the REF potential and ensure the sense resistor power rating matches the 100 mA maximum shunt current for reliable long-term operation.
Recommended
Voltage Supervisor and Threshold Comparator
Wired as a comparator with a 2.495V threshold, the TL431AQDBZRQ1 provides low-cost overvoltage or undervoltage detection for automotive ECUs, industrial controllers, and IoT nodes. A divider scales the monitored rail to the REF pin; when the threshold is crossed, the cathode pulls low and can directly drive an LED, a logic input, or a MOSFET gate for load disconnect. The fast shunt response and 0.2 ohm output impedance give a sharp transition edge, and the AEC-Q100 rating plus 36V maximum cathode voltage allow direct monitoring of automotive 12V rails with appropriate division. Add hysteresis via a small feedback resistor from cathode to REF to prevent chatter near the threshold.
Recommended
Industrial Power Supply Regulation
In industrial 24V systems, the TL431AQDBZRQ1 serves both as a shunt reference for setting rails between 2.5V and 36V and as the error amplifier in secondary-side regulation of AC-DC and DC-DC modules. Its -40C to +125C operation exceeds most industrial requirements, and the automotive qualification provides margin for harsh factory-floor environments. Typical implementations combine the TL431-Q1 with an optocoupler for galvanically isolated feedback or use it standalone as an adjustable 5V/12V shunt reference for op-amp rails and sensor bridges. Designers must respect the 100 mA cathode limit and provide a bias resistor sized for regulation current plus optocoupler LED drive, typically 2-5 mA.
Recommended
Battery Charger and Power-Bank Circuits
Portable and automotive battery-charger designs use the TL431AQDBZRQ1 as the voltage-set element in both linear and switch-mode charger feedback loops. The adjustable range (2.5V to 36V) covers one-cell Li-ion (4.2V), lead-acid (13.8V), and multi-cell string charging thresholds set with a two-resistor divider on REF. Its ±1% accuracy limits cell-voltage error, and the low 1 mA minimum cathode current keeps quiescent drain negligible in always-on charging supervision. In USB power-bank boost converters, the TL431-Q1 pairs with an optocoupler or a discrete feedback transistor to regulate the 5V output. Include a small-signal compensation capacitor from cathode to REF to keep the charging loop stable across load steps.
Recommended
Recommended Products Summary
Engineering reference data for TL431AQDBZRQ1 — comparison, design guidance, and compliance information.
Selection Guide
Comparison with Alternatives
| Parameter | This Product | TL431BQDBZRQ1 | TL431LIQDBZRQ1 | KA431AZTA | AZ431ANTR-E1 |
|---|---|---|---|---|---|
| Package | SOT-23 (DBZ), 3-pin | SOT-23 (DBZ), 3-pin - same | SOT-23 (DBZ), 3-pin - same | SOT-23, 3-pin - same | SOT-23, 3-pin - same |
| Brand | Texas Instruments | Texas Instruments | Texas Instruments | onsemi | Diodes Incorporated |
| Max Cathode Voltage | 36 V | 36 V | 36 V | 36 V | 36 V |
| Max Cathode Current | 100 mA | 100 mA | 100 mA | 100 mA | 100 mA |
| Automotive AEC-Q100 | Yes (Q1) | Yes (Q1) | Yes (Q1) | Verify per order code | No (commercial grade) |
| Key Advantage | Automotive qualified, 1% accuracy, industry-standard | Tighter 0.5% accuracy | Lower Iref and drift, better stability | Second-source availability | Second-source availability |
Key Differentiators
- Automotive AEC-Q100 qualification with extended temperature range (vs LM431ACM3)
- Balanced cost/accuracy at 1% (A grade) (vs TL431BQDBZRQ1)
- Standard reference input current for moderate-impedance dividers (vs TL431LIQDBZRQ1)
Design Notes
Guarantee a minimum cathode current of about 1 mA at all times; below this the TL431AQDBZRQ1 leaves regulation and the output voltage drifts. Size the bias resistor so that regulation current plus optocoupler LED current (typically 2-5 mA total) is available at minimum input voltage, while keeping peak current under the 100 mA absolute maximum. Estimated: for a 12V cathode bias and 2.5V reference feedback node, a 4.7 kohm bias resistor gives roughly 2 mA of cathode current.
Do not confuse TL431 and TL432 pinouts in the DBZ package - TI states the TL432 has a different pinout for the DBZ/DBV/PK packages, so a footprint wired for TL431 will not function with TL432 parts. Also verify REF divider resistor values: with very high resistor values, the reference input current (Iref) creates a voltage error; the TL431LI-Q1 with lower Iref mitigates this in high-impedance dividers.
Place the REF divider resistors directly at the REF pin and route the feedback sense trace away from switching nodes to avoid injecting ripple into the reference comparator. Keep the cathode-anode loop (bias resistor, optocoupler LED) short. For loop stability in optocoupler feedback designs, add an RC network from cathode to REF; the standard TI application circuit uses roughly 6.8 kohm series and a compensation capacitor sized to the optocoupler CTR and load capacitance.
Compliance Information
Green RoHS-compliant package per digchip specification listing; AEC-Q100 qualified per TI TL431-Q1 product page.
