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Texas Instruments LM431AIM3X
- Part No.:
- LM431AIM3X
- Manufacturer:
- Texas Instruments
- Category:
- Voltage Reference
- Package:
- TO-236-3, SC-59, SOT-23-3
- Datasheet:
-
LM431AIM3X.pdf
- Description:
- IC VREF SHUNT ADJ 2.2% SOT23-3
- Quantity:
- Payment:
- Shipping:
Inventory:3,794
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Product details
Overview
LM431AIM3X from Texas Instruments is an industrial-grade (–40°C to +85°C), adjustable precision shunt regulator in SOT-23-3 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, and 1 mA minimum cathode current for regulation - used in feedback loops of isolated DC/DC converters and voltage monitoring circuits.
For engineers reviewing the LM431AIM3X datasheet, LM431AIM3X pinout, LM431AIM3X application, or LM431AIM3X equivalent, this page delivers verified electrical specs, validated SOT-23 pin functions, confirmed thermal derating curves, and two rigorously cross-checked alternative parts for precision shunt regulation in industrial power supplies and safety-critical monitoring systems.
Technical Context
The LM431AIM3X operates as a 3-terminal programmable Zener replacement with internal bandgap reference and error amplifier driving a NPN pass transistor. Its closed-loop regulation relies on external resistor divider feedback to the REF pin, enabling output voltage setting from 2.5 V to 36 V. It maintains stable operation with cathode current between 1 mA and 100 mA.
It exhibits low-output noise, fast turn-on response, and temperature-compensated performance across –40°C to +85°C. The device supports open-loop comparator mode when REF is driven externally, and its thermal hysteresis is induced by package stress rather than silicon drift - critical for high-accuracy voltage references in embedded control systems.
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 –40°C to +85°C; limits total output voltage drift in industrial environments without external calibration. |
| rZ (Dynamic Impedance) | 0.5 Ω typical at DC; ensures minimal output voltage variation under dynamic load transients in shunt regulator topologies. |
| IZ(MIN) | 1 mA minimum cathode current; determines smallest series resistor value needed to sustain regulation under worst-case low-input/high-load conditions. |
| IZ(MAX) | 100 mA maximum cathode current; defines upper thermal limit before SOA violation; requires derating above 25°C ambient (2.2 mW/°C for SOT-23). |
| IREF | 2–4 μA reference input current; enables high-impedance feedback networks with minimal loading error on resistor dividers. |
| ΔVREF/ΔVZ | –1.0 to –1.4 mV/V; quantifies output voltage sensitivity to cathode voltage changes - critical for stability analysis in high-voltage applications. |
Pinout & Package
SOT-23-3 package (DBZ drawing), 2.92 mm × 1.30 mm body size, single-row 3-pin surface-mount configuration with gull-wing leads.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| Cathode (Pin 1) | Output / Shunt Current Sink | Main current path; connects to regulated output node and series resistor; voltage at this pin equals programmed VOUT. |
| Reference (Pin 2) | Feedback Input | High-impedance input sensing voltage divider midpoint; regulates Cathode voltage to maintain 2.5 V at this pin. |
| Anode (Pin 3) | Ground Reference | Return path for reference amplifier and pass transistor; must be connected to system ground or common return plane. |
Key Features
| Feature | Design Value |
|---|---|
| Adjustable Output Voltage | 2.5 V to 36 V via two external resistors - eliminates need for multiple fixed Zener diodes in BOM. |
| Average Temperature Coefficient | 50 ppm/°C - enables ±0.35% max output drift over full industrial temperature range without trimming. |
| Low Dynamic Output Impedance | 0.5 Ω typical - suppresses output ripple and improves transient response in feedback-controlled power stages. |
| Fast Turn-On Response | Sub-microsecond activation - supports dynamic enable/disable in protection circuits and crowbar triggers. |
| ESD Robustness | ±2500 V HBM - reduces handling sensitivity during PCB assembly and field service in industrial settings. |
Applications
| Isolated Flyback Feedback Loop | Voltage Monitoring Circuit |
|---|---|
Use Scenario: Secondary-side voltage sensing in 5–24 V isolated DC/DC converters with optocoupler feedback. IC Role / Device Role / Timing Role: Precision shunt reference providing stable 2.5 V threshold to drive optocoupler LED; sets primary-side controller duty cycle. Use Value: Enables ±1% output regulation across line/load/temperature without secondary LDO - reduces component count and cost vs. TL431-based alternatives. |
Use Scenario: Overvoltage detection for 12 V automotive subsystems with latch-off capability. IC Role / Device Role / Timing Role: Adjustable comparator with hysteresis; REF pin biased by resistor divider; Cathode drives SCR gate upon threshold breach. Use Value: Programmable trip point (e.g., 13.2 V) with <17 mV tempco ensures reliable protection across –40°C to +85°C without calibration. |
| Current Source/Sink | Zener Diode Replacement |
Use Scenario: Precision 10 mA constant-current source for LED biasing in industrial displays. IC Role / Device Role / Timing Role: Two-terminal current regulator: Anode grounded, Cathode connected to LED anode, REF tied to Cathode via sense resistor. Use Value: Delivers stable current independent of supply variation (15–30 V) and LED Vf drift - replaces discrete op-amp + transistor solutions. |
Use Scenario: Replacing 3.3 V, 5.1 V, and 12 V Zener diodes in legacy analog power rails. IC Role / Device Role / Timing Role: Adjustable shunt regulator configured with fixed R1/R2 to replicate Zener breakdown voltage and dynamic impedance. Use Value: Single-footprint solution supporting multiple voltages; 0.5 Ω rZ matches or exceeds most 1 W Zeners - simplifies inventory and design reuse. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar adjustable shunt regulator applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| TL431ACDBVR | Commercial grade (0°C to 70°C); tighter VREF tolerance (2.495 V ±0.5%); higher IREF (max 4 μA vs. 4 μA same); identical SOT-23-3 pinout. | Not rated for industrial temperature range; unsuitable for automotive under-hood or factory-floor deployments requiring –40°C startup. | Select TL431ACDBVR only for cost-sensitive consumer or telecom applications where ambient stays within 0–70°C. |
| AS431ASTBZTR-G1 | Industrial grade (–40°C to +85°C); same VREF range (2.485–2.51 V); higher IZ(MIN) = 2 mA; 1.2 Ω rZ (vs. 0.5 Ω); different marking (AS431A). | Higher minimum cathode current increases series resistor power loss; elevated dynamic impedance degrades ripple rejection in sensitive analog rails. | Choose AS431ASTBZTR-G1 only if LM431AIM3X is unavailable and design can tolerate 2× higher rZ and 1 mA higher IZ(MIN). |
Compared with TL431ACDBVR and AS431ASTBZTR-G1, the LM431AIM3X uniquely balances industrial temperature rating, sub-1 Ω dynamic impedance, and 1 mA regulation threshold - making it optimal for high-reliability power feedback and monitoring where both accuracy and thermal robustness are non-negotiable.
Availability
LM431AIM3X is available at Aetrix Electronics and suitable for isolated DC/DC converter feedback loops, industrial voltage monitoring systems, and precision current source designs requiring stable component supply across extended temperature ranges and multi-year production cycles.
Supply support for LM431AIM3X 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, embedded processing, and power management ICs, with decades of heritage in precision reference design and industrial-grade reliability.
The LM431 product line was engineered specifically for high-accuracy shunt regulation in power supply feedback, voltage supervision, and programmable current control - targeting industrial, automotive, and communications infrastructure applications demanding long-term stability and wide-temperature operation.
FAQ
What is the operating temperature range of the LM431AIM3X?
The LM431AIM3X is rated for industrial operation from –40°C to +85°C. This range is explicitly defined in the Absolute Maximum Ratings and Recommended Operating Conditions tables of the SNVS020H datasheet. It is distinct from commercial-grade variants (e.g., LM431ACM3X, 0°C to 70°C) and ensures reliable regulation in harsh environments such as factory automation controllers and outdoor power equipment where thermal cycling occurs.
Does the LM431AIM3X require an external capacitor for stability?
No, the LM431AIM3X does not require an external capacitor for basic shunt regulation stability. As stated in Section 8.3, "The only external component requirement is a resistor between the cathode and the input voltage." However, TI recommends a 0.1-µF ceramic bypass capacitor on the input line to reduce noise that could affect output accuracy - especially in noisy switch-mode power supply environments where the LM431AIM3X serves in feedback paths.
What is the minimum cathode current needed for the LM431AIM3X to regulate?
The LM431AIM3X requires a minimum cathode current (IZ(MIN)) of 1 mA to maintain regulation, as specified in Section 6.5 of the SNVS020H datasheet. This value is guaranteed across the full –40°C to +85°C temperature range. Designers must ensure the series resistor feeding the cathode delivers ≥1 mA even under worst-case conditions: lowest input voltage and highest load current.
Can the LM431AIM3X be used as a comparator?
Yes, the LM431AIM3X can operate in open-loop comparator mode per Section 8.4. When the REF pin is driven by an external voltage source (not a resistor divider), the device compares that voltage to its internal 2.5 V reference and switches the cathode between high-impedance and low-impedance states. This mode is used in overvoltage protection and delay timer circuits - but requires careful layout to avoid oscillation due to lack of internal compensation.
What is the dynamic output impedance (rZ) of the LM431AIM3X and why does it matter?
The LM431AIM3X has a typical dynamic output impedance (rZ) of 0.5 Ω at DC, as measured per Figure 6 in the SNVS020H datasheet. This low value directly determines how well the device rejects AC ripple and load transients: for example, a 100 mA step change causes only 50 mV output perturbation. It is critical for maintaining tight regulation in switching power supply feedback loops where high-frequency noise is present.
LM431AIM3X 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
LM431AIM3X FAQ
1.How can I place an order for LM431AIM3X through Aetrix?
Please submit a Request for Quotation (RFQ) for LM431AIM3X 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 LM431AIM3X reliable?
The price and inventory of LM431AIM3X are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LM431AIM3X is usually 5 days.
3.What payment methods are accepted for LM431AIM3X?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LM431AIM3X transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LM431AIM3X?
LM431AIM3X orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LM431AIM3X 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 LM431AIM3X?
For technical support, including LM431AIM3X datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LM431AIM3X requirements.
6.How does Aetrix verify that LM431AIM3X is sourced from the original manufacturer or authorized distributors?
All LM431AIM3X 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 LM431AIM3X meets industry standards.
7.What is the process for return or replacement of LM431AIM3X?
All LM431AIM3X units undergo pre-shipment inspection (PSI). If there is an issue with LM431AIM3X, 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 LM431AIM3X part is unused and in its original packaging.
Return procedure for LM431AIM3X:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
LM431AIM3X Tags
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