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Texas Instruments LM431AIZ/LFT1
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- Part No.:
- LM431AIZ/LFT1
- Manufacturer:
- Texas Instruments
- Category:
- Voltage Reference
- Package:
- TO-226-3, TO-92-3 (TO-226AA) Formed Leads
- Datasheet:
-
LM431AIZ/LFT1.pdf
- Description:
- IC VREF SHUNT ADJ 2.2% TO92-3
- Quantity:
- Payment:
- Shipping:
Inventory:3,448
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Product details
Overview
LM431AIZ/LFT1 from Texas Instruments is a precision adjustable shunt voltage regulator in TO-92 package, featuring 2.485 V to 2.51 V reference voltage (VREF), ±17 mV reference voltage deviation over temperature, 0.5 Ω typical dynamic output impedance, 1 mA minimum cathode current for regulation, and operation up to 36 V cathode voltage - used in feedback loops of linear/switching power supplies and voltage monitoring circuits.
For engineers reviewing the LM431AIZ/LFT1 datasheet, LM431AIZ/LFT1 pinout, LM431AIZ/LFT1 application, or LM431AIZ/LFT1 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 LM431AIZ/LFT1 operates as a 3-terminal programmable shunt regulator: its reference pin senses a divided fraction of cathode voltage, triggering internal amplification to adjust shunt current and maintain precise output regulation. It functions in closed-loop mode with external resistor dividers or open-loop comparator mode with independent reference drive.
Its architecture ensures stable regulation across –40°C to +85°C industrial temperature range, with average temperature coefficient of 50 ppm/°C and low-output noise enabling high-accuracy references. Thermal hysteresis is induced by package stress, not circuit design, and requires board-level thermal management per RθJA = 162.4 °C/W.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| VREF | 2.485–2.51 V at 10 mA; defines minimum programmable output voltage and sets accuracy baseline for external resistor divider. |
| VREF Deviation | ±17 mV over full temperature range; limits total output voltage drift in precision feedback applications. |
| rZ (Dynamic Impedance) | 0.5 Ω typical at DC; maintains tight regulation under load transients without external compensation. |
| IZ(MIN) | 1 mA minimum cathode current; determines smallest usable series resistor value in shunt regulator designs. |
| Cathode Voltage Range | 2.5 V to 36 V; enables direct replacement of Zener diodes in wide-input-voltage power supply feedback paths. |
| Reference Input Current | 2–4 μA; imposes negligible loading on feedback resistors, preserving divider ratio accuracy. |
| ESD Rating (HBM) | ±2500 V; requires standard ESD handling but no special protection circuitry in PCB layout. |
Pinout & Package
LM431AIZ/LFT1 uses TO-92 (LP) package: 4.30 mm × 4.30 mm body, 3-pin through-hole configuration with 0.1 inch lead pitch. Thermal resistance is RθJA = 162.4 °C/W; derating required above 25°C ambient.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| Cathode (Pin 1) | Output voltage node / shunt current sink | Connected to regulated output rail; carries full load + shunt current; must handle up to 100 mA. |
| Reference (Pin 2) | Feedback input / precision voltage sense | Connects to resistor divider midpoint; draws only 2–4 μA; sensitive to noise and layout parasitics. |
| Anode (Pin 3) | Ground return / current source reference | Typically tied to system ground; completes shunt current path; not floating or biased. |
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. |
| Temperature Compensation | Ensured stability over –40°C to +85°C with 50 ppm/°C avg. tempco - suitable for industrial-grade power supplies. |
| Fast Turnon Response | Sharp turnon characteristic enables rapid regulation recovery after line/load transients - critical for crowbar and OVP circuits. |
| Low-Dynamic Output Impedance | 0.5 Ω typical rZ minimizes output voltage sag during current steps - reduces need for large output capacitance. |
| Space-Saving TO-92 Package | Standard through-hole footprint with 4.3 mm × 4.3 mm body - compatible with legacy manual assembly and wave soldering. |
Applications
| Switch-Mode Power Supply Feedback | Overvoltage Protection (OVP) |
|---|---|
|
Use Scenario: Used in secondary-side feedback loop of isolated flyback or forward converters to regulate output voltage via optocoupler interface. IC Role / Device Role / Timing Role: Precision shunt regulator providing stable 2.5 V reference to drive optocoupler LED; sets regulation threshold independent of primary-side controller. Use Value: Enables ±1% output voltage accuracy across line/load/temperature; replaces discrete Zener + transistor networks with single-component solution. |
Use Scenario: Monitors DC bus voltage in motor drives or battery systems; triggers shutdown when exceeding safe threshold. IC Role / Device Role / Timing Role: Adjustable voltage comparator with hysteresis; reference pin set to trip point, cathode connected to latch or gate driver. Use Value: Programmable trip point from 2.5 V to 36 V allows reuse across platforms; fast turnon ensures sub-microsecond response to overvoltage events. |
| Current Sink Circuit | Voltage Monitor with Hysteresis |
|
Use Scenario: Provides constant current to LEDs, sensors, or bias networks in instrumentation and analog front-ends. IC Role / Device Role / Timing Role: Shunt regulator configured as two-terminal current sink; anode grounded, cathode/resistor tied to supply. Use Value: Delivers stable current independent of supply variation (within 36 V limit); 1 mA minimum IZ enables low-current operation down to ~2.5 mA total. |
Use Scenario: Detects brownout or overvoltage conditions in microcontroller power rails with built-in hysteresis to prevent chatter. IC Role / Device Role / Timing Role: Dual-threshold monitor using resistor network and capacitor timing; reference pin driven by RC-filtered supply. Use Value: Eliminates need for dedicated supervisor IC; hysteresis derived from LM431AIZ/LFT1's inherent thermal behavior and external component selection. |
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 | Wider VREF tolerance (2.45–2.55 V), higher max cathode current (100 mA vs. 100 mA same), identical TO-92 package and pinout. | Commercial-grade (0°C to 70°C) vs. LM431AIZ/LFT1's industrial –40°C to +85°C rating. | Select TL431ACZ for cost-sensitive commercial designs where extended temperature range is unnecessary. |
| LM431BIZ | Tighter VREF (2.485–2.51 V same), lower VREF deviation (±8 mV vs. ±17 mV), same TO-92 package and industrial temp range. | Higher precision reference for metrology or calibration circuits requiring <0.5% total error budget. | Choose LM431BIZ when reference stability dominates system accuracy and ±8 mV VREF deviation is mandatory. |
Compared with TL431ACZ and LM431BIZ, LM431AIZ/LFT1 offers balanced precision and industrial temperature capability at mid-tier cost - optimal for power supply feedback and OVP where ±17 mV VREF drift is acceptable and –40°C operation is required.
Availability
LM431AIZ/LFT1 is available at Aetrix Electronics and suitable for switching power supply feedback, overvoltage protection, and current sink circuits requiring stable component supply across industrial temperature ranges and long production lifecycles.
Supply support for LM431AIZ/LFT1 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 founded in 1930, specializing in analog and embedded processing technologies with broad portfolio coverage and rigorous automotive/industrial qualification standards.
LM431AIZ/LFT1 belongs to TI's precision shunt regulator product line, designed specifically for high-accuracy voltage reference and feedback applications in power conversion, protection, and sensing systems.
FAQ
What is the reference voltage tolerance of LM431AIZ/LFT1?
The LM431AIZ/LFT1 has a reference voltage (VREF) range of 2.485 V to 2.51 V at 10 mA, corresponding to ±0.5% initial accuracy. This tolerance is specified for the 'A' grade variant and remains stable over the full –40°C to +85°C operating temperature range, making LM431AIZ/LFT1 suitable for industrial applications demanding consistent regulation performance.
Can LM431AIZ/LFT1 replace a standard Zener diode?
Yes, LM431AIZ/LFT1 can directly replace many Zener diodes in shunt regulator and voltage reference applications. Unlike passive Zeners, LM431AIZ/LFT1 provides sharp turnon, low dynamic impedance (0.5 Ω), and temperature-compensated reference voltage - delivering superior regulation accuracy, especially across temperature extremes and varying load conditions.
What is the maximum cathode voltage rating for LM431AIZ/LFT1?
The absolute maximum cathode voltage for LM431AIZ/LFT1 is 37 V, with recommended operating range up to 36 V. Exceeding 37 V risks permanent damage. In practice, designs should maintain margin below 36 V to ensure reliability under transient conditions, particularly when used in feedback loops of off-line switchers or high-voltage DC systems.
Does LM431AIZ/LFT1 require external capacitors for stability?
No, LM431AIZ/LFT1 does not require external capacitors for basic regulation stability. However, TI recommends a 0.1 µF ceramic bypass capacitor near the cathode pin to suppress high-frequency noise that could affect regulation accuracy - especially in noisy switcher environments or long PCB traces.
How is thermal performance characterized for LM431AIZ/LFT1?
LM431AIZ/LFT1 in TO-92 package has a junction-to-ambient thermal resistance (RθJA) of 162.4 °C/W. At 25°C ambient, it supports up to 0.78 W internal power dissipation; above 25°C, derating is required at 6.2 mW/°C. Proper heatsinking or airflow is essential in high-current (>50 mA) or high-ambient applications to avoid thermal shutdown or parameter drift.
LM431AIZ/LFT1 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:
- -40°C ~ 85°C (TA)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Through Hole
- Supplier Device Package:
- TO-92-3
LM431AIZ/LFT1 FAQ
1.How can I place an order for LM431AIZ/LFT1 through Aetrix?
Please submit a Request for Quotation (RFQ) for LM431AIZ/LFT1 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 LM431AIZ/LFT1 reliable?
The price and inventory of LM431AIZ/LFT1 are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LM431AIZ/LFT1 is usually 5 days.
3.What payment methods are accepted for LM431AIZ/LFT1?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LM431AIZ/LFT1 transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LM431AIZ/LFT1?
LM431AIZ/LFT1 orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LM431AIZ/LFT1 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 LM431AIZ/LFT1?
For technical support, including LM431AIZ/LFT1 datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LM431AIZ/LFT1 requirements.
6.How does Aetrix verify that LM431AIZ/LFT1 is sourced from the original manufacturer or authorized distributors?
All LM431AIZ/LFT1 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 LM431AIZ/LFT1 meets industry standards.
7.What is the process for return or replacement of LM431AIZ/LFT1?
All LM431AIZ/LFT1 units undergo pre-shipment inspection (PSI). If there is an issue with LM431AIZ/LFT1, 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 LM431AIZ/LFT1 part is unused and in its original packaging.
Return procedure for LM431AIZ/LFT1:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
LM431AIZ/LFT1 Tags
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