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Texas Instruments LM431ACZ/LFT4
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- Part No.:
- LM431ACZ/LFT4
- Manufacturer:
- Texas Instruments
- Category:
- Voltage Reference
- Package:
- TO-226-3, TO-92-3 (TO-226AA) Formed Leads
- Datasheet:
-
LM431ACZ/LFT4.pdf
- Description:
- IC VREF SHUNT ADJ 2.2% TO92-3
- Quantity:
- Payment:
- Shipping:
Inventory:1,974
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Product details
Overview
LM431ACZ/LFT4 from Texas Instruments is a 3-terminal adjustable precision shunt regulator with 2.485 V to 2.51 V reference voltage (VREF), ±17 mV max reference deviation over temperature, and 0.5 Ω typical dynamic output impedance. It operates from 2.5 V to 36 V output range and supports 1 mA to 100 mA cathode current in TO-92 package for voltage monitoring and linear power supply feedback circuits.
For engineers reviewing the LM431ACZ/LFT4 datasheet, LM431ACZ/LFT4 pinout, LM431ACZ/LFT4 application, or LM431ACZ/LFT4 equivalent, this page delivers verified electrical specs, TO-92 terminal mapping, real-world use cases in overvoltage protection and current sinking, and two validated alternative parts with documented functional and thermal differences.
Technical Context
The LM431ACZ/LFT4 implements a bandgap-based precision reference with internal error amplifier and NPN pass transistor, enabling stable shunt regulation across –40°C to 85°C industrial temperature range. Its reference input draws only 2–4 μA and exhibits 50 ppm/°C average temperature coefficient.
It functions in closed-loop mode via external resistor divider (R1/R2) to set output voltage VO = VREF × (1 + R1/R2), requiring minimum 1 mA cathode current for regulation and supporting fast turnon response for transient-sensitive applications like crowbar circuits.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| VREF | 2.485–2.51 V at 25°C - defines minimum programmable output voltage and sets accuracy baseline for external resistor network |
| VREF Deviation | ±17 mV over full temperature range - determines worst-case output voltage drift in precision feedback loops |
| rZ (Dynamic Impedance) | 0.5 Ω typical - ensures low AC output impedance for stable regulation under varying load transients |
| Cathode Current Range | 1–100 mA - defines usable shunt current window; below 1 mA regulation fails, above 100 mA risks thermal overload in TO-92 |
| Reference Input Current | 2–4 μA - enables high-impedance feedback networks without loading error, critical for battery-powered monitors |
| Temperature Range | –40°C to +85°C - qualified for industrial environments where ambient thermal cycling impacts reference stability |
| Package Thermal Resistance | RθJA = 162.4°C/W - limits maximum power dissipation to ~460 mW at 25°C ambient before junction exceeds 150°C |
Pinout & Package
LM431ACZ/LFT4 uses TO-92 package (4.30 mm × 4.30 mm body), rated for 0.78 W internal power dissipation at 25°C ambient with 6.2 mW/°C derating above that temperature.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| Anode (Pin 3) | Ground reference node | Internally connected to substrate; must be tied to system ground for proper reference biasing and thermal path |
| Cathode (Pin 1) | Shunt current output / regulated voltage node | Connects to output rail; sinks variable current to maintain programmed voltage; carries full load + shunt current |
| Reference (Pin 2) | Feedback input | High-impedance input sensing divided output voltage; 2–4 μA bias current flows here, enabling precise resistor ratio setting |
Key Features
| Feature | Design Value |
|---|---|
| Adjustable Output Voltage | Programmable from 2.5 V to 36 V using two external resistors - eliminates need for multiple fixed Zener diodes |
| Low Dynamic Output Impedance | 0.5 Ω typical - maintains tight voltage regulation during rapid load changes in switching power supply feedback paths |
| Fast Turnon Response | Enables use in crowbar and overvoltage shutdown circuits - responds quickly to fault conditions without external delay components |
| Temperature Compensation | Ensured stability over full –40°C to +85°C range - avoids calibration drift in industrial temperature monitoring systems |
| Low-Output Noise | Minimal broadband noise contribution - preserves signal integrity in precision analog measurement front-ends |
Applications
| Overvoltage Protection | Voltage Monitoring |
|---|---|
Use Scenario: Detects when DC bus voltage exceeds safe threshold (e.g., 12 V rail rising to 15 V due to regulator failure). IC Role / Device Role / Timing Role: Acts as precision comparator triggering SCR gate or MOSFET gate driver to short circuit or disable supply. Use Value: Provides ±17 mV reference stability over temperature, ensuring consistent trip point without recalibration across operating environment. |
Use Scenario: Monitors battery voltage in portable medical device to initiate low-power warning at 3.3 V. IC Role / Device Role / Timing Role: Serves as adjustable threshold detector with high-impedance reference input minimizing battery drain. Use Value: 2–4 μA reference current enables multi-year operation on coin cell; TO-92 footprint fits space-constrained PCB layouts. |
| Current Sink Circuit | Zener Diode Replacement |
Use Scenario: Provides constant 20 mA sink for LED backlight in automotive infotainment display. IC Role / Device Role / Timing Role: Configured as two-resistor current source with cathode tied to LED anode and anode grounded. Use Value: 0.5 Ω dynamic impedance ensures <1% current variation across 9–16 V input range, improving luminance consistency. |
Use Scenario: Replaces 5.1 V Zener in legacy power supply feedback loop where tighter tolerance and lower tempco are required. IC Role / Device Role / Timing Role: Functions as programmable shunt reference with identical 3-pin TO-92 mounting and cathode/anode polarity. Use Value: 50 ppm/°C tempco vs. typical 100–200 ppm/°C for Zeners reduces output drift by >50% over –40°C to +85°C. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar adjustable shunt regulator applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| TL431ACZ | Same 2.495 V nominal VREF but wider 2.45–2.55 V tolerance; 0.75 Ω rZ; 100 mA max cathode current; TO-92 package | Higher reference tolerance and higher dynamic impedance reduce accuracy in precision feedback loops | Select TL431ACZ only when cost sensitivity outweighs need for ±17 mV VREF stability and 0.5 Ω rZ performance |
| LM431AIM3X/NOPB | SOT-23-3 package; same VREF spec (2.485–2.51 V); –40°C to +85°C rating; 0.28 W power dissipation limit | Smaller footprint but lower thermal capability - unsuitable for >150 mW continuous dissipation applications | Choose LM431AIM3X/NOPB for space-constrained designs where peak power stays below 120 mW and board area is premium |
Compared with TL431ACZ and LM431AIM3X/NOPB, LM431ACZ/LFT4 offers superior reference stability (±17 mV vs. ±25 mV) and lower dynamic impedance (0.5 Ω vs. 0.75 Ω), making it optimal for industrial voltage monitors and high-accuracy shunt regulators where thermal margin and long-term drift matter most.
Availability
LM431ACZ/LFT4 is available at Aetrix Electronics and suitable for industrial voltage monitoring, overvoltage protection circuits, and precision current sink designs requiring stable component supply across extended temperature ranges and multi-year production cycles.
Supply support for LM431ACZ/LFT4 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 company specializing in analog and embedded processing technologies, with leadership in precision analog ICs and power management solutions.
LM431ACZ/LFT4 belongs to TI's precision shunt regulator product line, designed specifically for industrial-grade voltage reference, feedback, and protection applications where temperature stability and long-term accuracy are critical.
FAQ
What is the reference voltage tolerance of LM431ACZ/LFT4?
The LM431ACZ/LFT4 has a reference voltage (VREF) range of 2.485 V to 2.51 V at 25°C, corresponding to ±10 mV absolute tolerance. Over the full –40°C to +85°C operating range, VREF deviation is specified at ±17 mV, ensuring predictable performance in industrial thermal environments. This specification is confirmed in Section 6.5 of the SNVS020H datasheet.
Can LM431ACZ/LFT4 replace a standard Zener diode directly?
Yes, LM431ACZ/LFT4 can directly replace many Zener diodes in shunt regulator configurations due to its identical 3-pin TO-92 package, anode/cathode/reference pinout, and ability to operate down to 2.5 V. Unlike passive Zeners, it requires only two external resistors to set output voltage and provides superior temperature stability (50 ppm/°C vs. 100–200 ppm/°C) and lower dynamic impedance (0.5 Ω vs. 10–50 Ω).
What is the maximum power dissipation for LM431ACZ/LFT4 in TO-92 package?
LM431ACZ/LFT4 has a maximum internal power dissipation of 0.78 W at 25°C ambient, with thermal derating of 6.2 mW/°C above 25°C. At 85°C ambient, maximum allowable dissipation drops to approximately 0.41 W. This limit is defined by RθJA = 162.4°C/W and TJ(max) = 150°C, per Section 6.1 and 6.4 of the datasheet.
How does the reference input current affect circuit design with LM431ACZ/LFT4?
The reference input current of LM431ACZ/LFT4 is 2–4 μA at 25°C and increases to ≤1.2 μA over temperature. This low bias current allows use of high-value feedback resistors (e.g., 100 kΩ–1 MΩ), minimizing quiescent power draw in battery-powered voltage monitors while avoiding significant voltage division error - a key advantage over op-amp-based references requiring mA-level supply current.
Is LM431ACZ/LFT4 suitable for crowbar circuit applications?
Yes, LM431ACZ/LFT4 is explicitly used in crowbar circuits (Figure 20 of SNVS020H). Its fast turnon response, sharp knee characteristic, and ability to sink up to 100 mA make it ideal for triggering thyristors or MOSFETs during overvoltage events. The TO-92 package provides mechanical robustness for transient surge handling, and its –40°C to +85°C rating ensures reliability in industrial power systems.
LM431ACZ/LFT4 Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Texas Instruments
- Package/Case:
- TO-226-3, TO-92-3 (TO-226AA) Formed Leads
- Series:
- -
- Packaging:
- Tape & Reel (TR)
- 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/LFT4 FAQ
1.How can I place an order for LM431ACZ/LFT4 through Aetrix?
Please submit a Request for Quotation (RFQ) for LM431ACZ/LFT4 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/LFT4 reliable?
The price and inventory of LM431ACZ/LFT4 are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LM431ACZ/LFT4 is usually 5 days.
3.What payment methods are accepted for LM431ACZ/LFT4?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LM431ACZ/LFT4 transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LM431ACZ/LFT4?
LM431ACZ/LFT4 orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LM431ACZ/LFT4 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/LFT4?
For technical support, including LM431ACZ/LFT4 datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LM431ACZ/LFT4 requirements.
6.How does Aetrix verify that LM431ACZ/LFT4 is sourced from the original manufacturer or authorized distributors?
All LM431ACZ/LFT4 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/LFT4 meets industry standards.
7.What is the process for return or replacement of LM431ACZ/LFT4?
All LM431ACZ/LFT4 units undergo pre-shipment inspection (PSI). If there is an issue with LM431ACZ/LFT4, 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/LFT4 part is unused and in its original packaging.
Return procedure for LM431ACZ/LFT4:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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