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Texas Instruments LM431AIM3
- Part No.:
- LM431AIM3
- Manufacturer:
- Texas Instruments
- Category:
- Voltage Reference
- Package:
- TO-236-3, SC-59, SOT-23-3
- Datasheet:
-
LM431AIM3.pdf
- Description:
- IC VREF SHUNT ADJ 2.2% SOT23-3
- Quantity:
- Payment:
- Shipping:
Inventory:8,277
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Product details
Overview
LM431AIM3 from Texas Instruments is an adjustable precision shunt regulator IC with 2.5 V reference voltage, ±17 mV reference voltage deviation over temperature, 0.75 Ω typical dynamic output impedance, 1 mA minimum cathode current for regulation, and industrial-grade −40°C to +85°C operating range - used in feedback loops of isolated DC-DC converters and voltage monitoring circuits.
For engineers reviewing the LM431AIM3 datasheet, LM431AIM3 pinout, LM431AIM3 application, or LM431AIM3 equivalent, this page delivers verified electrical specs, SOT-23 package mapping, functional role in closed-loop regulation, thermal derating guidance, and validated alternative parts for precision shunt reference design.
Technical Context
The LM431AIM3 operates as a 3-terminal programmable Zener replacement, using internal bandgap reference and transconductance amplifier to maintain stable cathode voltage via shunt current control. Its reference pin senses external resistor divider output, enabling output voltage programming from 2.5 V to 36 V.
It functions in closed-loop mode (reference tied to output via R1/R2) with 1–100 mA cathode current range, or open-loop comparator mode with independent reference biasing. Temperature-compensated architecture achieves 50 ppm/°C average tempco and <17 mV total reference drift across −40°C to +85°C.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Reference voltage (VREF) | 2.485–2.51 V at 25°C - defines minimum programmable output and sets accuracy baseline for feedback networks |
| Reference voltage deviation | ±17 mV over full −40°C to +85°C range - determines worst-case output tolerance without external trimming |
| Dynamic output impedance | 0.75 Ω typical at DC - enables low-noise regulation and fast transient response in shunt configurations |
| Minimum cathode current | 0.4–1 mA - sets lower bound for RS resistor sizing to ensure regulation under light/no-load conditions |
| Cathode voltage range | 2.5 V to 36 V - defines maximum output programmability and input headroom requirements for series resistor |
| Reference input current | 2–4 μA - enables high-impedance feedback dividers without significant loading error |
| ESD rating (HBM) | ±2500 V - informs handling precautions during PCB assembly and bench testing |
Pinout & Package
SOT-23 (DBZ) 3-pin surface-mount package with 2.92 mm × 1.30 mm body size, moisture sensitivity level 1 (260°C peak reflow), and lead-free (RoHS & no Sb/Br) finish.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| Cathode (Pin 1) | Output / Shunt current sink | Connected to regulated output node; carries total load + shunt current; voltage referenced to Anode |
| Reference (Pin 2) | Feedback sense input | High-impedance node tied to resistor divider midpoint; triggers regulation when voltage reaches ~2.5 V |
| Anode (Pin 3) | Ground reference / return path | Typically connected to system ground; serves as common reference for cathode and reference pins |
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-stable reference | Average tempco of 50 ppm/°C and ≤17 mV total drift over −40°C to +85°C - ensures consistent regulation across environmental stress |
| Low dynamic output impedance | 0.75 Ω typical - maintains tight output regulation under varying load and line conditions without external compensation |
| Fast turn-on response | Sub-microsecond activation - supports dynamic load switching and protection circuitry requiring rapid voltage clamping |
| Low-output noise | Specified with low-noise internal topology - reduces ripple injection into sensitive analog or feedback paths |
Applications
| Isolated Flyback Converter Feedback | Voltage Monitoring Circuit |
|---|---|
Use Scenario: Secondary-side voltage sensing in optocoupler-coupled flyback power supplies. IC Role / Device Role / Timing Role: Precision shunt reference providing stable 2.5 V threshold to drive optocoupler LED, enabling primary-side regulation. Use Value: Maintains ±1% output accuracy across temperature and line variations without secondary-side LDO. |
Use Scenario: Overvoltage detection on 12 V automotive rail before ECU power entry. IC Role / Device Role / Timing Role: Adjustable threshold comparator with hysteresis via external resistor network. Use Value: Triggers crowbar or shutdown at precisely 13.2 V using R1 = 10 kΩ, R2 = 2.2 kΩ - replaces discrete Zener + transistor solution. |
| Current Sink for LED Biasing | Zener Diode Replacement in Linear Regulator |
Use Scenario: Constant-current source for calibration-grade LED test fixtures. IC Role / Device Role / Timing Role: Shunt-regulated current sink with cathode grounded and reference biased to set current via Rsense. Use Value: Delivers 20 mA ±0.5% over 0–70°C using 125 Ω sense resistor - eliminates thermal drift of standard Zener-based sinks. |
Use Scenario: Output voltage setting element in three-terminal linear regulator feedback loop. IC Role / Device Role / Timing Role: Programmable reference replacing fixed 6.2 V Zener to adjust output from 5 V to 15 V. Use Value: Enables single BOM variant for multiple output voltages with <1% initial error and no trim pot required. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar adjustable shunt reference applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| TL431CDBVR | Commercial-grade (0°C to 70°C), tighter 2.495 V reference (±0.5%), higher 100 mA max cathode current | Not rated for industrial temperature range; better suited for cost-sensitive consumer power supplies | Select TL431CDBVR only if ambient stays within 0–70°C and tighter initial accuracy is prioritized over temperature stability |
| AS431ASTU | Same industrial −40°C to +85°C range, 2.5 V reference (±1%), but 1.5 Ω typical dynamic impedance vs. 0.75 Ω | Higher output impedance limits use in high-bandwidth feedback loops or low-noise references | Choose AS431ASTU where RoHS+REACH compliance and long-term supply continuity outweigh dynamic impedance requirements |
Compared with LM431AIM3, TL431CDBVR trades industrial temperature capability for tighter initial accuracy and higher current drive, while AS431ASTU matches the temperature grade but sacrifices dynamic impedance performance - making LM431AIM3 optimal for thermally demanding, low-impedance shunt regulation.
Availability
LM431AIM3 is available at Aetrix Electronics and suitable for isolated DC-DC converter feedback, voltage monitoring, current sink circuits, and Zener diode replacement applications requiring stable component supply across extended temperature ranges.
Supply support for LM431AIM3 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 high-accuracy, temperature-stable shunt regulation in space-constrained power systems - targeting industrial, telecom, and automotive subsystems where Zener diodes lack stability or programmability.
FAQ
What is the operating temperature range of the LM431AIM3?
The LM431AIM3 is rated for industrial operation from −40°C to +85°C. This specification is confirmed in the TI datasheet's Recommended Operating Conditions table and distinguishes it from commercial-grade variants like the LM431ACM3. The device marking "N1E" on the SOT-23 package further validates its industrial qualification. LM431AIM3 maintains reference voltage stability and regulation integrity across this full range.
How does the LM431AIM3 differ from the LM431ACM3?
The LM431AIM3 and LM431ACM3 share identical electrical architecture but differ in temperature grade and packaging: LM431AIM3 is industrial (−40°C to +85°C) in SOT-23, while LM431ACM3 is commercial (0°C to 70°C) in the same SOT-23 package. Their reference voltage tolerances also differ - LM431AIM3 specifies 2.485–2.51 V, whereas LM431ACM3 is 2.47–2.52 V. LM431AIM3 is not a drop-in replacement for LM431ACM3 in thermally demanding environments.
What is the minimum cathode current required for regulation in the LM431AIM3?
The LM431AIM3 requires a minimum cathode current of 0.4–1 mA to maintain regulation, per the Electrical Characteristics table in the TI datasheet. This value is critical for calculating the maximum allowable series resistor (RS) in shunt regulator designs. Below this threshold, the device exits regulation and cathode voltage collapses. LM431AIM3's low IZ(MIN) enables efficient operation in low-power monitoring circuits.
Can the LM431AIM3 be used as a comparator?
Yes, the LM431AIM3 can operate in open-loop comparator mode by applying an external voltage to the reference pin while holding cathode and anode at fixed potentials. In this configuration, it switches sharply when the reference pin voltage crosses ~2.5 V. However, it lacks dedicated comparator features like push-pull output or rail-to-rail swing - so LM431AIM3 is best suited for slow, precision threshold detection rather than high-speed logic interfacing.
What is the dynamic output impedance of the LM431AIM3 and why does it matter?
The LM431AIM3 has a typical dynamic output impedance of 0.75 Ω at DC, measured between cathode and anode with reference pin biased. This low impedance ensures minimal output voltage variation under changing load or line conditions - critical for maintaining regulation accuracy in feedback loops and reducing noise coupling. Higher impedance would degrade transient response and increase sensitivity to PCB layout parasitics in LM431AIM3-based designs.
LM431AIM3 Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Texas Instruments
- Package/Case:
- TO-236-3, SC-59, SOT-23-3
- Series:
- -
- Packaging:
- Tape & Reel (TR)
- Product Status:
- Obsolete
- 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:
- Surface Mount
- Supplier Device Package:
- SOT-23-3
LM431AIM3 FAQ
1.How can I place an order for LM431AIM3 through Aetrix?
Please submit a Request for Quotation (RFQ) for LM431AIM3 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 LM431AIM3 reliable?
The price and inventory of LM431AIM3 are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LM431AIM3 is usually 5 days.
3.What payment methods are accepted for LM431AIM3?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LM431AIM3 transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LM431AIM3?
LM431AIM3 orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LM431AIM3 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 LM431AIM3?
For technical support, including LM431AIM3 datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LM431AIM3 requirements.
6.How does Aetrix verify that LM431AIM3 is sourced from the original manufacturer or authorized distributors?
All LM431AIM3 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 LM431AIM3 meets industry standards.
7.What is the process for return or replacement of LM431AIM3?
All LM431AIM3 units undergo pre-shipment inspection (PSI). If there is an issue with LM431AIM3, 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 LM431AIM3 part is unused and in its original packaging.
Return procedure for LM431AIM3:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
LM431AIM3 Tags
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TL431AIDBZR
Texas Instruments
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TL431BQDBZR
Texas Instruments
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AN431AN-ATRG1
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LM4040CYM3-2.5-TR
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LM4040CYM3-4.1-TR
Microchip Technology
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LM4040EIM3-2.5/NOPB
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AZ431LBNTR-G1
Diodes Incorporated
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LM4040D20IDBZR
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LM4041DIM3-ADJ/NOPB
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LM4040DIM3X-2.5/NOPB
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LM4040DIM3-2.5/NOPB
Texas Instruments
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AZ431LANTR-G1
Diodes Incorporated
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