TL431BMFDT - 2.495V Adjustable Shunt Regulator | Nexperia
N.º de pieza: TL431BMFDT ✓ Activo| Cant. | Precio unitario | Total |
|---|---|---|
| 1 | $0.28 | $0,28 |
| 10 | $0.21 | $2,10 |
| 100 | $0.13 | $13,00 |
| 500 | $0.1 | $50,00 |
| 1.000 | $0.08 | $80,00 |
TL431BMFDT Descripción general
A shunt regulator, also called a shunt voltage reference, is a two-state device that maintains a constant voltage across its terminals by sinking excess current. Within the power management hierarchy, it sits alongside bandgap references and series regulators as a fundamental building block for voltage monitoring, feedback loops, and precision thresholding. Because it behaves like an error amplifier with an integrated 2.495 V reference, the TL431 family is the de facto standard feedback element in isolated and non-isolated switching power supplies.
Key features include the tight 0.5% initial reference tolerance at 25C, the wide 36 V maximum cathode voltage, and a low dynamic output impedance. The TL431xBM series is qualified for automotive applications, and the device requires only about 1 mA of minimum cathode current for regulation in typical designs, keeping standby losses low.
Technically, the device integrates a 2.495 V bandgap reference, an internal op amp, and an open-collector output transistor. When the voltage at the reference pin exceeds 2.495 V, the cathode conducts and pulls the cathode pin toward the anode, making the part function as a single-supply comparator with a built-in precision reference. Temperature coefficient is approximately 888 ppm/C per third-party parameter listings.
Typical applications include optocoupler feedback in flyback and forward SMPS converters, adjustable voltage monitors and overvoltage crowbar triggers, precision current sources and sinks, and setpoint generation for battery charger circuits.
A key design consideration is stability: with certain cathode-to-reference capacitance ranges the loop can oscillate, so verify the recommended stability region in the Nexperia datasheet and add a compensation capacitor or series resistor if operating near the boundary.
This page synthesizes distributor pricing, drop-in cross-references, and practical design notes not found in the manufacturer datasheet.
Alternativas directas para TL431BMFDT — mismo encapsulado, compatible pin a pin. Se excluyen las piezas de otro encapsulado que requieren retrabajo de la PCB.
Variantes de esta serie
Modelos de la misma serie compatibles directamente con TL431BMFDT (mismo factor de forma y huella) — difiere en Operating Temperature Range, Package, Reference Voltage (Vref), Pinning Configuration.
Herramienta de comparación rápida — seleccione piezas alternativas para compararlas lado a lado:
TL431BFDT
✅ Sustitución directa ⚠️ Especificaciones sin verificar✓ En stock
$0.08 / unidad
Ver hoja de datos →TL431CFDT
✅ Sustitución directa ⚠️ Especificaciones sin verificar📋 Alternativa de referencia (no en el catálogo)
TL431AFDT
✅ Sustitución directa ⚠️ Especificaciones sin verificar📋 Alternativa de referencia (no en el catálogo)
TL431AIDBZR
✅ Sustitución directa✓ En stock
$0.08 / unidad
Ver hoja de datos →LM431CCM3/NOPB
✅ Sustitución directa📋 Alternativa de referencia (no en el catálogo)
KA431
✅ Sustitución directa📋 Alternativa de referencia (no en el catálogo)
AZ431
✅ Sustitución directa📋 Alternativa de referencia (no en el catálogo)
TL431BMFDT Especificaciones
| Product Type | Adjustable precision shunt regulator / voltage reference |
| Reference Voltage (Vref) | 2.495 V typical |
| Reference Tolerance at 25C | ±0.5% (B grade) |
| Adjustable Output Voltage Range | 2.495 V to 36 V |
| Maximum Cathode Current | 100 mA |
| Temperature Coefficient | 888 ppm/C |
| Rango de temperatura de funcionamiento | -40C to +125C |
| Temperature Grade | Q (automotive, -40C to +125C) |
| Encapsulado | SOT-23 (TO-236AB), 3-pin |
| Tipo de montaje | Surface Mount |
| Pinning Configuration | Normal (Ref / Anode / Cathode) |
| Application Segment | Automotive qualified |
| Topología | Bandgap reference + error amplifier + output transistor |
| Reference Voltage Range (Vref limits) | 2.48 V to 2.55 V |
| Estado RoHS | Compliant |
Configuración de pines de TL431BMFDT
| Pin 1 | REF — Reference input - output voltage setpoint sensing (nominal 2.495 V threshold) |
| Pin 2 | A — Anode - ground / lowest potential terminal |
| Pin 3 | K — Cathode - regulated output / current sink terminal (up to 100 mA) |
Aplicaciones típicas
TL431BMFDT es adecuado para 6 aplicacións: SMPS Optocoupler Feedback, Overvoltage Protection and Crowbar, Precision Current Source, Adjustable Voltage Reference for ADC/DAC Systems, Battery Charger Voltage Regulation, Zener Replacement and Level Shifting.
SMPS Optocoupler Feedback
The TL431BMFDT is the industry-standard error amplifier in isolated flyback and forward converter secondary-side feedback loops. Its 2.495 V reference and 0.5% tolerance set the output voltage setpoint with tight accuracy, while the open-collector output directly drives an optocoupler LED through a resistor, transferring the error signal across the isolation barrier. With the TL431xBM automotive grade rated to 125C, it survives hot secondary-side environments inside sealed adapters and chargers. Compensation (typically a resistor-capacitor network from cathode to reference) stabilizes the loop; the datasheet stability region must be observed to avoid oscillation with certain divider impedances.
Recomendado
Overvoltage Protection and Crowbar
Because the TL431BMFDT combines a 2.495 V precision reference with comparator-like behavior, it is ideal for overvoltage detection. A divider scales the monitored rail to the reference pin; when the rail exceeds the threshold, the cathode pulls low and can trigger a thyristor crowbar, drive a fault flag, or gate off a DC-DC converter. The 0.5% reference tolerance gives a predictable trip point, and the 36 V cathode rating allows monitoring of high-voltage buses directly with appropriate dividers. Its automotive -40C to +125C range suits battery-management and automotive rail supervision where transient overvoltage events must be caught reliably.
Recomendado
Precision Current Source
The TL431BMFDT forms simple, accurate current sources and current sinks: a sense resistor from anode to reference programs the current as I = 2.495 V / Rsense, with the cathode tied to the supply through a ballast resistor or to a PNP/P-MOSFET pass element. The 0.5% reference accuracy translates directly into current accuracy, outperforming simple zener-based circuits. This topology is common in LED bias, sensor excitation, and 4-20 mA loop transmitters. Power dissipation in the sense resistor and the SOT-23 package must be budgeted, since the device dissipates (Vka x Ika) during regulation.
Recomendado
Adjustable Voltage Reference for ADC/DAC Systems
For cost-sensitive data-converter circuits, the TL431BMFDT provides an adjustable precision reference fed from a higher supply rail through a series resistor. Buffering the cathode with an op amp yields a stiff reference for ADC or DAC inputs, while the 0.5% initial tolerance and low dynamic impedance keep setpoint error low. Operating up to 36 V cathode voltage allows referencing from industrial 24 V rails without pre-regulation. For high-resolution converters, add RC filtering to reduce reference noise and consider a dedicated low-noise series reference if noise-free resolution demands exceed what a shunt reference can deliver.
Recomendado
Battery Charger Voltage Regulation
In linear and switching battery chargers, the TL431BMFDT senses the battery terminal voltage through a divider and closes the regulation loop, clamping charge voltage at the programmed termination point such as 4.2 V for Li-ion cells. The 2.495 V reference and 0.5% tolerance support accurate termination, which directly affects cell longevity and safety. The automotive-grade temperature range tolerates enclosed charging environments, and the 100 mA cathode capability lets it drive modest gate-drive or status-indication loads directly. Combine with a current-limit element for complete CC/CV charging behavior.
Recomendado
Zener Replacement and Level Shifting
As a programmable zener, the TL431BMFDT replaces discrete zener diodes with far better tolerance (0.5% vs typical 5%) and a user-defined clamp voltage from 2.495 V to 36 V set by two resistors. This is valuable for level shifting, supply clamping, and threshold references in industrial I/O modules and sensor interfaces. Unlike a zener, its knee is sharp and its dynamic impedance is low, so regulation is tighter across current variations. The SOT-23 footprint occupies minimal board area, and the automotive qualification permits use in 24 V industrial and vehicle-level signal conditioning chains.
Recomendado
Resumen de productos recomendados
Datos de referencia de ingeniería para TL431BMFDT — comparación, orientación de diseño e información de cumplimiento.
Guía de selección
Comparación con alternativas
| Parámetro | Este producto | TL431BFDT | TL431AIDBZR | LM431CCM3/NOPB | KA431 | AZ431 |
|---|---|---|---|---|---|---|
| Package | SOT-23 (TO-236AB) | SOT-23 (TO-236AB) - same | SOT-23 (DBZ) - same footprint | SOT-23 (TO-236AB) - same | SOT-23 - same footprint | SOT-23 - same footprint |
| Brand | Nexperia | Nexperia | Texas Instruments | Texas Instruments | onsemi | Diodes Incorporated |
| Reference Voltage | 2.495 V | 2.495 V | 2.495 V | 2.495 V | 2.495 V | 2.495 V |
| Max Output Voltage | 36 V | 36 V | 36 V | 36 V | 36 V | 36 V |
| Max Cathode Current | 100 mA | 100 mA | 100 mA | 100 mA | 100 mA | 100 mA |
Diferenciadores clave
- Tightest tolerance in the FDT family (frente a TL431BFDT)
- Extended 125C automotive range (frente a TL431AIDBZR)
- Trade-off: tighter accuracy at potentially higher cost (frente a AZ431)
Notas de diseño
Stability is the most common TL431 design failure. The device can oscillate when the capacitance from cathode to reference falls in a critical range (roughly 0.01 uF to 10 uF depending on cathode current and divider impedance). Consult the Nexperia datasheet stability boundary curves: either keep the cathode-reference capacitance below the lower boundary, add a series resistor with a larger compensation capacitor, or place the compensation network from cathode to reference instead of cathode to anode for wide-bandwidth feedback loops.
Budget power dissipation explicitly: P = (Vka - Va) x Ika. In a 24 V-to-5 V rail monitor with 10 mA cathode current, the device dissipates roughly 190 mW, well within SOT-23 limits, but a 36 V crowbar at 50 mA approaches 1.8 W and will exceed the package. Estimated from the 100 mA / 36 V absolute ratings; verify against the derating curve for your board copper and ambient. Set cathode current above the minimum regulation current (typically about 1 mA) with margin for accuracy.
Keep the resistor divider as close to the REF pin as possible and use 1% or better resistors to preserve the 0.5% reference accuracy. In optocoupler feedback loops, place the TL431 near the optocoupler anode-side resistor to minimize the high-impedance error-node trace length, which is sensitive to switching-noise pickup from the transformer. A small ceramic capacitor across the output at the point of regulation reduces ripple fed into the divider.
Información de cumplimiento
RoHS compliant per Nexperia current product status. Automotive temperature class (Q, -40C to +125C) per Nexperia product overview. REACH/halogen-free status not stated in retrieved data - consult Nexperia material declarations.
