Texas Instruments LM431 – Adjustable Precision Shunt Regulator for Voltage Reference Applications
Le LM431 from Texas Instruments is a three-terminal adjustable shunt regulator that functions like a precision Zener diode with a sharp 2.5 V reference voltage and output voltage adjustable up to 36 V. This device offers excellent accuracy (±1% reference voltage tolerance) and is widely used in power management and control loops for high-performance analog systems.
Designed for versatility, the LM431 delivers consistent regulation in both isolated and non-isolated power topologies. It can be used as a low-cost voltage reference in switching power supplies, voltage monitors, or as a comparator with open-collector output. Its compact packaging in TO-92, SOT-23, and SOIC forms makes it ideal for board layouts with limited space.
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Spécifications techniques
| Paramètres | Valeur | Unité |
|---|---|---|
| Reference Voltage (VREF) | 2.495 ±1% | V |
| Plage de tension de sortie réglable | 2.5 to 36 | V |
| Dynamic Output Impedance | 0.22 (typ) | Ω |
| Output Current Range | 1 to 100 | mA |
| Température de fonctionnement | De -40 à +125 | °C |
| Options du paquet | TO-92, SOIC-8, SOT-23 | – |
Why Choose LM431 Over Standard Zener Diodes?
- Adjustability: Unlike fixed Zeners, the LM431 supports a wide range of voltages, ideal for designs needing multiple setpoints.
- Improved Line and Load Regulation: Dynamic output impedance ensures stable output under varying conditions.
- Haute précision : Tight reference tolerance enhances regulation precision in control loops.
- Compact and Flexible Packaging: Fits various layouts, including portable and modular power systems.
- Texas Instruments Quality: Ensures product consistency, longevity, and availability for industrial-grade use.
Applications typiques
- Voltage reference in isolated and non-isolated SMPS
- Adjustable precision regulator circuits
- Overvoltage/undervoltage protection
- Analog and digital power supplies
- Battery chargers and monitors
Texas Instruments Reliability & Support
As a product of Texas Instruments, the LM431 undergoes rigorous manufacturing and reliability standards, including AEC-Q100 qualification for automotive-grade designs. Its low cost and high precision make it a widely adopted solution across consumer electronics, industrial control, and power supply sectors. TI also offers simulation models, application notes, and evaluation modules to assist engineers in rapid deployment.
Foire aux questions (FAQ)
How is the LM431 different from a Zener diode?
Unlike Zener diodes with fixed voltage, the LM431 allows output adjustment from 2.5 V to 36 V using an external resistor divider, offering greater flexibility in regulated voltage design.
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Can LM431 be used in switching power supplies?
Yes. It is widely used in feedback control loops of SMPS circuits as a precision reference voltage to ensure output stability and regulation.
Does the LM431 require external components to set output voltage?
Yes. The output voltage is set using two external resistors in a voltage divider configuration, which allows designers to fine-tune regulation according to system needs.
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What are the limitations on current through LM431?
The LM431 supports cathode current from 1 mA to 100 mA. Operation outside this range can degrade performance or cause instability in voltage regulation.
Can I use LM431 for overvoltage protection?
Absolutely. It can be configured as a comparator to detect when voltages exceed a defined threshold, effectively triggering protection or shutdown circuits.
