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Texas Instruments LM431CIZ/LFT1
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- Part No.:
- LM431CIZ/LFT1
- Manufacturer:
- Texas Instruments
- Category:
- Voltage Reference
- Package:
- TO-226-3, TO-92-3 (TO-226AA) Formed Leads
- Datasheet:
-
LM431CIZ/LFT1.pdf
- Description:
- IC VREF SHUNT -0.6%/+0.4% TO92-3
- Quantity:
- Payment:
- Shipping:
Inventory:4,043
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Product details
Overview
LM431CIZ/LFT1 from Texas Instruments is a 3-terminal adjustable precision shunt regulator with 2.5 V reference voltage, ±17 mV reference voltage deviation over temperature, 0.5 Ω dynamic output impedance, 1 mA minimum cathode current for regulation, and TO-92 package for through-hole mounting in voltage monitoring and linear power supply feedback circuits.
For engineers reviewing the LM431CIZ/LFT1 datasheet, LM431CIZ/LFT1 pinout, LM431CIZ/LFT1 application, or LM431CIZ/LFT1 equivalent, this page delivers verified electrical parameters, TO-92 terminal mapping, thermal derating guidance, real-world shunt regulator design constraints, and validated alternative parts for industrial voltage reference and overvoltage protection use cases.
Technical Context
The LM431CIZ/LFT1 operates as a precision shunt regulator by comparing its internal 2.5 V bandgap reference against an external resistor divider connected to the Reference pin, then sinking variable cathode current to maintain stable output voltage. Its closed-loop operation requires 1–100 mA cathode current and supports output programming from 2.5 V to 36 V.
It features temperature-compensated bandgap reference circuitry ensuring 50 ppm/°C average temperature coefficient and low 0.5 Ω dynamic output impedance at DC, enabling stable regulation under load transients without external compensation in most configurations.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Reference Voltage (VREF) | 2.5 V nominal; tight 2.485–2.51 V tolerance at 25°C enables accurate output setting in feedback networks. |
| Reference Voltage Deviation | ±17 mV over full operating range (−40°C to +85°C); defines worst-case output error in precision references. |
| Dynamic Output Impedance | 0.5 Ω typical at DC; ensures minimal output voltage shift under fast load-current changes. |
| Minimum Cathode Current | 1 mA required to maintain regulation; sets lower bound on series resistor sizing in shunt designs. |
| Maximum Cathode Voltage | 36 V absolute max; defines upper limit of programmable output voltage range. |
| Reference Input Current | 2–4 μA typical; enables high-impedance feedback dividers without significant loading error. |
| Thermal Resistance (RθJA) | 162.4 °C/W (TO-92); requires derating above 25°C at 6.2 mW/°C for safe continuous operation. |
Pinout & Package
LM431CIZ/LFT1 uses the standard 3-pin TO-92 package (LP drawing), 4.30 mm × 4.30 mm body size, with leads arranged in straight-line configuration for through-hole PCB assembly.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| Anode | Ground reference node | Internally connected to substrate; must be tied to system ground for proper reference biasing. |
| Cathode | Shunt current output / regulated voltage node | Connects to output rail; sinks current to maintain set voltage; maximum 36 V rating. |
| Reference | Feedback input | Accepts voltage divider tap; regulates when voltage equals 2.5 V; draws only 2–4 μA. |
Key Features
| Feature | Design Value |
|---|---|
| Adjustable output voltage range | 2.5 V to 36 V via two external resistors - eliminates need for multiple fixed Zener diodes. |
| Temperature-stable reference | 50 ppm/°C average TC and ±17 mV total deviation over −40°C to +85°C - suitable for industrial environments. |
| Low dynamic output impedance | 0.5 Ω typical - maintains tight regulation during rapid load steps without added output capacitance. |
| Fast turn-on response | Sub-microsecond transition from OFF to regulation - supports transient-sensitive feedback loops. |
| Low-output noise | Typical <10 µVRMS in 10 Hz–10 kHz band - preserves signal integrity in precision analog systems. |
Applications
| Switch-Mode Power Supply Feedback | Voltage Monitoring Circuit |
|---|---|
Use Scenario: Used in optocoupler-coupled secondary-side feedback loop of isolated flyback converters. IC Role / Device Role / Timing Role: Adjustable shunt regulator providing precise 2.5 V reference to drive optocoupler LED current proportional to output voltage. Use Value: Enables ±1% output regulation across line/load/temperature without primary-side sensing components. |
Use Scenario: Detects overvoltage condition on a 12 V automotive rail before downstream IC damage occurs. IC Role / Device Role / Timing Role: Precision threshold comparator with hysteresis via external resistor network on Reference pin. Use Value: Triggers crowbar or shutdown at exactly 13.8 V ±0.1 V, avoiding false trips from ripple or noise. |
| Current Sink for LED Biasing | Zener Diode Replacement |
Use Scenario: Provides constant 20 mA sink for high-brightness indicator LEDs in industrial HMIs. IC Role / Device Role / Timing Role: Shunt regulator configured as two-terminal current source using single series resistor. Use Value: Delivers stable current independent of supply variation from 15 V to 24 V, eliminating LED brightness drift. |
Use Scenario: Replaces 5.1 V Zener diode in legacy linear regulator feedback path where tighter tolerance is needed. IC Role / Device Role / Timing Role: Programmable shunt reference substituting fixed-voltage Zener with 2.5 V reference and external divider. Use Value: Reduces output voltage error from ±5% (Zener) to ±0.4% (LM431CIZ/LFT1 + 0.1% resistors). |
Equivalent & Alternatives
The following parts are listed as comparable options for similar adjustable shunt regulator applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| TL431CDBZR | SOIC-8 package; 2.495 V reference (±0.5%); 0.22 Ω rZ; 100 mA max cathode current. | Surface-mount layout; higher current capability; better thermal performance in PCB-constrained designs. | Select TL431CDBZR when board space permits SMT and higher current (>100 mA) or lower impedance (<0.5 Ω) is required. |
| AS431ARTDT-33 | SOT-23-3 package; 2.5 V reference (±1%); 1.5 Ω rZ; 100 mA max cathode current; −40°C to +125°C rating. | Smaller footprint; wider temperature range; slightly higher impedance limits high-speed transient response. | Choose AS431ARTDT-33 for compact, extended-temp designs where TO-92 mechanical robustness is not mandatory. |
Compared with LM431CIZ/LFT1, TL431CDBZR offers superior thermal dissipation and lower impedance in SOIC-8, while AS431ARTDT-33 trades TO-92 mechanical reliability for SOT-23 miniaturization and extended temperature operation - both require revalidation of feedback divider and thermal layout.
Availability
LM431CIZ/LFT1 is available at Aetrix Electronics and suitable for industrial voltage monitoring, linear power supply feedback, and overvoltage protection circuits requiring stable component supply, long-term lifecycle support, and RoHS-compliant through-hole packaging.
Supply support for LM431CIZ/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 specializing in analog and embedded processing technologies, with leadership in precision analog ICs and power management solutions.
The LM431 product line was designed for cost-effective, high-accuracy voltage regulation in power supplies, battery chargers, and safety-critical monitoring systems - delivering Zener-grade simplicity with bandgap-level stability.
FAQ
What is the reference voltage tolerance of LM431CIZ/LFT1 over temperature?
The LM431CIZ/LFT1 has a reference voltage tolerance of ±17 mV over its full operating temperature range of −40°C to +85°C. This corresponds to a maximum deviation of ±0.68% from the nominal 2.5 V reference. The device achieves this via internal temperature compensation, resulting in an average temperature coefficient of 50 ppm/°C - confirmed in Section 6.5 of the SNVS020H datasheet.
Can LM431CIZ/LFT1 replace a standard Zener diode directly?
Yes, LM431CIZ/LFT1 can directly replace many Zener diodes in shunt regulator applications, but requires two external resistors to set the output voltage instead of relying on fixed breakdown voltage. Its 2.5 V reference enables precise programmability from 2.5 V to 36 V, and its sharp turn-on characteristic minimizes regulation error - making it especially effective where Zener voltage drift or poor temperature stability is problematic.
What is the minimum cathode current required for regulation in LM431CIZ/LFT1?
The LM431CIZ/LFT1 requires a minimum cathode current of 1 mA to maintain regulation, as specified in the Electrical Characteristics table (IZ(MIN) parameter). Below this threshold, the device exits regulation and output voltage collapses. This value is critical for sizing the series resistor (RS) in shunt configurations - particularly under worst-case conditions of minimum input voltage and maximum load current.
How does the TO-92 package affect thermal performance of LM431CIZ/LFT1?
The TO-92 package of LM431CIZ/LFT1 has a junction-to-ambient thermal resistance (RθJA) of 162.4 °C/W. At 25°C ambient, its maximum allowable power dissipation is 0.78 W, but must be derated by 6.2 mW/°C above 25°C. This limits continuous operation in high-power shunt roles unless heatsinking or airflow is added - unlike SOIC or SOT-23 variants with lower RθJA values.
Is LM431CIZ/LFT1 suitable for overvoltage protection circuits?
Yes, LM431CIZ/LFT1 is widely used in overvoltage protection circuits, such as crowbar triggers and comparator-based shutdown systems. Its precise 2.5 V reference and low input bias current (2–4 μA) allow accurate threshold setting with high-resistance feedback networks, minimizing quiescent power. Application examples including Figure 20 (Crow Bar) and Figure 21 (Over/Under Voltage Protection) are documented in the SNVS020H datasheet.
LM431CIZ/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:
- Obsolete
- Reference Type:
- Shunt
- Output Type:
- Adjustable
- Voltage - Output (Min/Fixed):
- 2.5V
- Voltage - Output (Max):
- 37 V
- Current - Output:
- 100 mA
- Tolerance:
- -0.6%, +0.4%
- 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
LM431CIZ/LFT1 FAQ
1.How can I place an order for LM431CIZ/LFT1 through Aetrix?
Please submit a Request for Quotation (RFQ) for LM431CIZ/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 LM431CIZ/LFT1 reliable?
The price and inventory of LM431CIZ/LFT1 are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LM431CIZ/LFT1 is usually 5 days.
3.What payment methods are accepted for LM431CIZ/LFT1?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LM431CIZ/LFT1 transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LM431CIZ/LFT1?
LM431CIZ/LFT1 orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LM431CIZ/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 LM431CIZ/LFT1?
For technical support, including LM431CIZ/LFT1 datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LM431CIZ/LFT1 requirements.
6.How does Aetrix verify that LM431CIZ/LFT1 is sourced from the original manufacturer or authorized distributors?
All LM431CIZ/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 LM431CIZ/LFT1 meets industry standards.
7.What is the process for return or replacement of LM431CIZ/LFT1?
All LM431CIZ/LFT1 units undergo pre-shipment inspection (PSI). If there is an issue with LM431CIZ/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 LM431CIZ/LFT1 part is unused and in its original packaging.
Return procedure for LM431CIZ/LFT1:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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