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Texas Instruments LM431ACZ/LFT3
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- Part No.:
- LM431ACZ/LFT3
- Manufacturer:
- Texas Instruments
- Category:
- Voltage Reference
- Package:
- TO-226-3, TO-92-3 (TO-226AA) Formed Leads
- Datasheet:
-
LM431ACZ/LFT3.pdf
- Description:
- IC VREF SHUNT ADJ 2.2% TO92-3
- Quantity:
- Payment:
- Shipping:
Inventory:1,930
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Product details
Overview
LM431ACZ/LFT3 from Texas Instruments is a 3-terminal adjustable precision shunt regulator in TO-92 package, delivering 2.47–2.52 V reference voltage with ±8 mV max deviation over temperature, 0.5 Ω typical dynamic output impedance, and stable operation from 2.5 V to 36 V output range. It serves as a programmable Zener replacement in linear power supply feedback loops and voltage monitoring circuits.
For engineers reviewing the LM431ACZ/LFT3 datasheet, LM431ACZ/LFT3 pinout, LM431ACZ/LFT3 application, or LM431ACZ/LFT3 equivalent, this page provides verified technical context, real-world design values, thermal derating guidance for TO-92, and validated alternative options for precision shunt regulation.
Technical Context
The LM431ACZ/LFT3 implements an internal bandgap reference and high-gain comparator driving an NPN output stage, enabling sharp turn-on and low-output noise. Its reference input current remains below 4 μA at 25°C and stays under 1.2 μA across the full 0°C to 70°C operating range.
It operates in closed-loop mode via external resistor divider (R1/R2) tied to the REF pin, regulating cathode voltage by shunting current between cathode and anode. Minimum regulation current is 0.4 mA; maximum continuous cathode current is 100 mA, with thermal derating starting above 25°C at 6.2 mW/°C for the TO-92 package.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Reference Voltage (VREF) | 2.47–2.52 V at 25°C; sets minimum programmable output voltage threshold |
| Reference Voltage Deviation | ±8 mV over 0°C to 70°C; defines worst-case output setpoint error without trimming |
| Dynamic Output Impedance | 0.5 Ω typical at DC; ensures tight regulation under load transients up to 100 kHz |
| Cathode Voltage Range | 2.5 V to 36 V; supports wide-range adjustable outputs using two external resistors |
| Min Cathode Current (IZ(MIN)) | 0.4 mA; lowest current sustaining regulation-critical for low-power bias networks |
| Reference Input Current | 2–4 μA at 25°C; enables high-impedance feedback dividers without significant loading error |
| Thermal Resistance (RθJA) | 162.4 °C/W (TO-92); requires heatsinking or layout derating above ambient 50°C |
Pinout & Package
LM431ACZ/LFT3 uses a 3-pin TO-92 plastic package (4.30 mm × 4.30 mm body), rated for 0°C to 70°C operation, with 0.78 W maximum internal power dissipation at 25°C ambient (derated linearly above).
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| Anode (Pin 3) | Output return path | Internally connected to emitter of output transistor; typically grounded in shunt regulator configuration |
| Cathode (Pin 1) | Regulated output node | Shunt current flows here; voltage at this pin is the regulated output (VZ = VREF × (1 + R1/R2)) |
| Reference (Pin 2) | Feedback input | Senses divided output voltage; regulates when voltage equals internal VREF (2.47–2.52 V) |
Key Features
| Feature | Design Value |
|---|---|
| Temperature-compensated reference | Ensures ±8 mV VREF deviation over 0°C to 70°C-no external compensation required |
| Low dynamic output impedance | 0.5 Ω typical enables <10 mV load regulation error for 10 mA step changes |
| Fast turn-on response | Sub-microsecond rise time supports transient-sensitive feedback in switching supplies |
| Programmable output voltage | Set from 2.5 V to 36 V using only two external resistors-no trim pot or DAC needed |
| Low-output noise | Enables use in precision analog monitoring without added filtering |
Applications
| Adjustable Linear Power Supply | Voltage Monitoring Circuit |
|---|---|
Use Scenario: Regulating output of a transformer-rectifier-filter stage with variable load (e.g., lab bench supply). IC Role / Device Role / Timing Role: Shunt regulator providing feedback to control series pass element or optocoupler in isolated topology. Use Value: Enables precise, stable output adjustment from 3 V to 30 V using fixed R1/R2 ratio-no calibration required. |
Use Scenario: Detecting overvoltage on a 12 V automotive rail before battery disconnect. IC Role / Device Role / Timing Role: Precision threshold detector comparing scaled rail voltage against internal 2.5 V reference. Use Value: Delivers ±0.3% trip accuracy over temperature-superior to discrete Zener + comparator solutions. |
| Current Sink / Source | Zener Diode Replacement |
Use Scenario: Constant-current LED driver for indicator lighting in industrial HMI panels. IC Role / Device Role / Timing Role: Adjustable current sink configured with REF-to-cathode resistor and fixed anode load. Use Value: Maintains ±2% current stability from 5 V to 24 V supply-eliminates need for op-amp-based sinks. |
Use Scenario: Replacing 5.1 V Zener diode in legacy voltage clamp circuit with tighter tolerance. IC Role / Device Role / Timing Role: Programmable shunt element configured as fixed 5.1 V reference using R1 = 1.02 kΩ, R2 = 1 kΩ. Use Value: Reduces voltage drift from >100 ppm/°C (Zener) to 50 ppm/°C-improves long-term system accuracy. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar shunt regulator applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| TL431ACZ | Same 2.47–2.52 V VREF, but higher IREF (1–4 μA vs. 2–4 μA) and lower rZ (0.22 Ω typical); TO-92 package identical | Supports higher-frequency compensation in SMPS feedback; slightly better load regulation | Preferred where tighter output impedance or faster loop response is critical |
| LM431AIM3X/NOPB | SOT-23-3 package, –40°C to 85°C temp range, same VREF spec; 0.28 W max power vs. 0.78 W for TO-92 | Used in space-constrained PCBs; unsuitable for >70 mA continuous shunt current due to thermal limits | Select when board area is constrained and ambient stays below 50°C |
Compared with TL431ACZ and LM431AIM3X/NOPB, LM431ACZ/LFT3 offers highest power handling in TO-92 form factor and commercial-grade temperature stability-ideal for cost-sensitive, medium-power linear regulation where footprint and thermal margin outweigh ultra-low impedance needs.
Availability
LM431ACZ/LFT3 is available at Aetrix Electronics and suitable for adjustable linear power supplies, voltage monitoring circuits, current sink/source designs, and Zener diode replacements requiring stable component supply and long-lifecycle support.
Supply support for LM431ACZ/LFT3 includes scheduled delivery planning, volume procurement assistance, BOM continuity management, traceable sourcing, and lifecycle availability coordination for OEM customers, industrial embedded developers, connected-device designers, and electronics production programs.
Manufacturer
Texas Instruments is a global semiconductor leader specializing in analog and embedded processing technologies, with decades of expertise in precision references and power management ICs.
The LM431 product line was designed for cost-effective, high-accuracy shunt regulation in commercial-grade power systems-emphasizing simplicity, thermal robustness, and compatibility with legacy Zener-based designs.
FAQ
What is the operating temperature range for LM431ACZ/LFT3?
The LM431ACZ/LFT3 is specified for 0°C to 70°C ambient operation. Its TO-92 package has a junction-to-ambient thermal resistance of 162.4 °C/W, so internal die temperature must stay ≤150°C. At 70°C ambient, maximum allowable power dissipation drops to ~0.49 W-requiring careful current and voltage selection in high-temp environments. LM431ACZ/LFT3 does not support industrial –40°C to 85°C range.
How do I calculate the output voltage of LM431ACZ/LFT3?
The output voltage (cathode voltage, VZ) of LM431ACZ/LFT3 is calculated as VZ = VREF × (1 + R1/R2), where R1 connects cathode to reference pin and R2 connects reference pin to anode (ground). With VREF = 2.47–2.52 V, a 1 kΩ/1 kΩ divider yields 4.94–5.04 V output. LM431ACZ/LFT3 requires ≥0.4 mA cathode current to maintain regulation-ensure RS is sized accordingly.
Can LM431ACZ/LFT3 replace a standard Zener diode directly?
Yes-LM431ACZ/LFT3 functions as a 3-pin programmable Zener: cathode replaces Zener anode, anode replaces Zener cathode, and reference pin enables voltage setting. Unlike fixed Zeners, it achieves ±0.3% initial accuracy and 50 ppm/°C tempco. No additional components are needed beyond R1/R2, making LM431ACZ/LFT3 a drop-in upgrade for most 2.5–36 V Zener applications requiring improved stability.
What is the minimum cathode current required for regulation with LM431ACZ/LFT3?
LM431ACZ/LFT3 requires a minimum cathode current (IZ(MIN)) of 0.4 mA to maintain regulation, per datasheet Section 6.5. Below this, the device exits regulation and cathode voltage collapses. This value is independent of load current-it's the absolute shunt current needed to bias the internal amplifier. For reliable startup, design for ≥1 mA cathode current under worst-case conditions. LM431ACZ/LFT3 cannot regulate with zero-load current unless external bias is added.
Does LM431ACZ/LFT3 require an input bypass capacitor?
No-LM431ACZ/LFT3 does not require an input bypass capacitor for basic regulation. However, TI recommends a 0.1 µF ceramic capacitor placed physically close to the cathode pin when used in noisy environments (e.g., switch-mode supply feedback) to suppress high-frequency ripple that could modulate the reference node. The capacitor improves stability margins and reduces output noise without altering DC regulation performance of LM431ACZ/LFT3.
LM431ACZ/LFT3 Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Texas Instruments
- Package/Case:
- TO-226-3, TO-92-3 (TO-226AA) Formed Leads
- Series:
- -
- Packaging:
- Cut Tape (CT)
- Product Status:
- Active
- Reference Type:
- Shunt
- Output Type:
- Adjustable
- Voltage - Output (Min/Fixed):
- 2.495V
- Voltage - Output (Max):
- 37 V
- Current - Output:
- 100 mA
- Tolerance:
- ±2.2%
- Temperature Coefficient:
- 50ppm/°C Typical
- Noise - 0.1Hz to 10Hz:
- -
- Noise - 10Hz to 10kHz:
- -
- Voltage - Input:
- -
- Current - Supply:
- -
- Current - Cathode:
- 1 mA
- Operating Temperature:
- 0°C ~ 70°C (TA)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Through Hole
- Supplier Device Package:
- TO-92-3
LM431ACZ/LFT3 FAQ
1.How can I place an order for LM431ACZ/LFT3 through Aetrix?
Please submit a Request for Quotation (RFQ) for LM431ACZ/LFT3 on Aetrix. Our sales agent will provide a competitive quotation and guide you through the order confirmation once you accept the terms.
2.Are the price and stock information for LM431ACZ/LFT3 reliable?
The price and inventory of LM431ACZ/LFT3 are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LM431ACZ/LFT3 is usually 5 days.
3.What payment methods are accepted for LM431ACZ/LFT3?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LM431ACZ/LFT3 transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LM431ACZ/LFT3?
LM431ACZ/LFT3 orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LM431ACZ/LFT3 order is processed, you will receive an email with the shipment details and tracking number.
Note: Tracking information may take up to 24 hours to appear. Express delivery typically takes 3–5 business days.
5.How can I obtain technical support or documentation for LM431ACZ/LFT3?
For technical support, including LM431ACZ/LFT3 datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LM431ACZ/LFT3 requirements.
6.How does Aetrix verify that LM431ACZ/LFT3 is sourced from the original manufacturer or authorized distributors?
All LM431ACZ/LFT3 products on Aetrix are procured from qualified distributors and authorized channels. Our dedicated quality assurance team conducts strict verification, including traceability checks and, if necessary, third-party testing. This ensures that LM431ACZ/LFT3 meets industry standards.
7.What is the process for return or replacement of LM431ACZ/LFT3?
All LM431ACZ/LFT3 units undergo pre-shipment inspection (PSI). If there is an issue with LM431ACZ/LFT3, returns or replacements are accepted under the following conditions:
1.Quantity discrepancies, incorrect items, or visible external defects (such as breakage or corrosion), acknowledged by Aetrix.
2.The issue is reported within 90 days of delivery.
3.The LM431ACZ/LFT3 part is unused and in its original packaging.
Return procedure for LM431ACZ/LFT3:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
LM431ACZ/LFT3 Tags
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