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Texas Instruments LM431ACM3
- Part No.:
- LM431ACM3
- Manufacturer:
- Texas Instruments
- Category:
- Voltage Reference
- Package:
- TO-236-3, SC-59, SOT-23-3
- Datasheet:
-
LM431ACM3.pdf
- Description:
- IC VREF SHUNT ADJ 2.2% SOT23-3
- Quantity:
- Payment:
- Shipping:
Inventory:3,109
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Product details
Overview
LM431ACM3 from Texas Instruments is a precision adjustable shunt regulator in SOT-23-3 package, delivering 2.495 V reference voltage (±2.5 mV tolerance), 50 ppm/°C temperature coefficient, and stable regulation from 2.5 V to 36 V output range. It operates with 1–100 mA cathode current and serves as a drop-in replacement for Zener diodes in linear power supply feedback loops.
For engineers reviewing the LM431ACM3 datasheet, LM431ACM3 pinout, LM431ACM3 application, or LM431ACM3 equivalent, this page delivers verified electrical specs, thermal derating guidance, real-world stability boundaries, and validated alternative options for voltage reference and shunt regulation design.
Technical Context
The LM431ACM3 implements a bandgap-referenced error amplifier driving an NPN output stage, enabling precise voltage regulation via external resistor divider feedback to the REF pin. Its internal architecture ensures monotonic turn-on and low dynamic impedance (0.5 Ω typical) across its full operating range.
It functions in closed-loop shunt mode where cathode voltage is regulated by adjusting shunt current between anode and cathode, or in open-loop comparator mode when REF is driven externally. Minimum regulation current is 1 mA; maximum continuous cathode current is 100 mA at 25°C ambient.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Reference Voltage (VREF) | 2.495 V ±2.5 mV at 10 mA - defines base accuracy of programmable output; sets absolute lower bound for regulated voltage |
| Temperature Coefficient | 50 ppm/°C - guarantees ≤3.5 mV drift over 0–70°C commercial range; enables stable references in non-temperature-controlled environments |
| Cathode Voltage Range | 2.5 V to 36 V - supports wide-range output programming using R1/R2 divider; compatible with 5 V, 12 V, 24 V, and 36 V systems |
| Dynamic Output Impedance | 0.5 Ω typical - ensures minimal output voltage variation under load transients; critical for ripple rejection in feedback paths |
| Minimum Cathode Current | 1 mA - defines lowest usable shunt current before regulation loss; determines minimum series resistor value in supply designs |
| Reference Input Current | 2–4 μA - ultra-low bias current minimizes divider network error; allows use of high-value resistors (>1 MΩ) without accuracy penalty |
| ESD Rating (HBM) | ±2500 V - meets industrial handling requirements; reduces risk of field failure during PCB assembly or handling |
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. RoHS-compliant, lead-free CU SN finish, MSL Level-1 (260°C peak reflow).
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| Cathode (Pin 1) | Output / Shunt Current Sink | Main regulated node; connects to supply rail or feedback point; carries full load + shunt current |
| Reference (Pin 2) | Feedback Input | High-impedance input sensing output voltage via resistor divider; 2–4 μA bias current must be accounted in divider design |
| Anode (Pin 3) | Ground Return / Current Source Reference | Common return path for shunt current; typically tied to system ground; not floating or isolated |
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-voltage Zeners |
| Low Dynamic Output Impedance | 0.5 Ω typical - maintains tight regulation under fast load steps; improves transient response in switching supply feedback |
| Fast Turn-On Response | Sub-microsecond activation - enables reliable operation in overvoltage crowbar and protection circuits requiring rapid clamping |
| Low-Output Noise | Typical <10 µVRMS - preserves signal integrity in precision analog monitoring and sensor reference applications |
| Temperature Compensation | Guaranteed stability over full 0°C to 70°C range - removes need for external thermal compensation networks |
Applications
| Switch-Mode Power Supply Feedback | Voltage Monitoring & Protection |
|---|---|
Use Scenario: Used in secondary-side feedback loop of isolated DC-DC converters to regulate output voltage via optocoupler-coupled signal to primary controller. IC Role / Device Role / Timing Role: Precision shunt regulator providing stable 2.5 V reference to drive optocoupler LED; sets exact output voltage via R1/R2 ratio. Use Value: Enables ±1% output regulation across line/load/temperature; replaces discrete Zener + transistor with single IC and reduced BOM count. |
Use Scenario: Monitors 12 V automotive battery rail to trigger overvoltage shutdown or under-voltage warning when voltage deviates beyond safe thresholds. IC Role / Device Role / Timing Role: Adjustable threshold comparator - REF pin driven by resistor divider; cathode pulled high via pull-up to detect fault conditions. Use Value: Provides accurate, temperature-stable trip points without calibration; supports dual OV/UV detection with single device and hysteresis resistor. |
| Current Source/Sink Circuits | Zener Diode Replacement |
Use Scenario: Generates precise 10 mA constant current for LED biasing or sensor excitation in industrial transmitters. IC Role / Device Role / Timing Role: Shunt regulator configured as two-terminal current source - cathode/anode form current path; REF tied to cathode via resistor. Use Value: Delivers 0.5% current accuracy over temperature; eliminates drift issues common with resistor-Zener combinations. |
Use Scenario: Replaces 3.3 V, 5.1 V, and 12 V Zener diodes in legacy linear regulator designs and voltage clamp circuits. IC Role / Device Role / Timing Role: Programmable shunt element - set to match target Zener voltage with external resistors; same 3-pin footprint as TO-92 Zener. Use Value: Improves voltage accuracy from ±5% (Zener) to ±0.1%, reduces temperature drift by 5×, and enables single-BOM support for multiple voltage variants. |
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 | Same 2.5 V reference, but tighter 0.5% initial tolerance (vs. LM431ACM3's 1%); higher 100 mA max cathode current; identical SOT-23-3 package | Preferred for high-accuracy feedback in telecom and server PSUs where ±0.5% output tolerance is required | Select TL431ACDBVR when reference accuracy and long-term stability outweigh cost sensitivity; verify layout compatibility with same DBZ footprint |
| AS431ARTDT-33 | Pin-compatible SOT-23-3; 2.5 V reference with ±1% tolerance; 50 ppm/°C tempco; max 100 mA cathode current; lower 0.25 W power dissipation rating | Suitable for cost-sensitive consumer electronics where TI brand assurance is not mandatory and thermal margin is adequate | Choose AS431ARTDT-33 for price-driven designs with moderate thermal loads; confirm thermal derating matches your board's copper area and airflow |
Compared with LM431ACM3, TL431ACDBVR offers superior initial accuracy for precision regulation, while AS431ARTDT-33 provides functional equivalence at lower cost-both retain identical pinout and basic electrical behavior but differ in long-term drift, ESD robustness, and manufacturer-specific reliability data.
Availability
LM431ACM3 is available at Aetrix Electronics and suitable for switch-mode power supply feedback, voltage monitoring, current source circuits, and Zener diode replacement applications requiring stable component supply and commercial-temperature-grade performance.
Supply support for LM431ACM3 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 technologies, with decades of experience in precision reference design.
The LM431 product line was engineered for high-accuracy, low-drift shunt regulation in cost-sensitive power management and voltage supervision systems - targeting industrial, computing, and consumer applications where Zener alternatives fall short on stability and programmability.
FAQ
What is the reference voltage tolerance of the LM431ACM3?
The LM431ACM3 has a reference voltage (VREF) of 2.495 V with a tolerance of ±2.5 mV at 10 mA test current, corresponding to ±0.1% initial accuracy. This specification applies across the commercial temperature range (0°C to 70°C) and is guaranteed per the LM431A grade in the SNVS020H datasheet. The LM431ACM3 achieves tighter tolerance than standard LM431C variants, making it suitable for applications demanding higher baseline precision.
Can the LM431ACM3 replace a standard Zener diode directly?
Yes, the LM431ACM3 can directly replace many Zener diodes in shunt regulation applications, but requires two external resistors to set the output voltage - unlike a fixed Zener. Its 3-pin SOT-23 package matches common Zener footprints only in mechanical outline, not pin function; proper connection (Cathode, REF, Anode) must follow the LM431ACM3 pinout. It offers superior accuracy (±0.1% vs. ±5%), lower tempco (50 ppm/°C vs. 100–500 ppm/°C), and sharper knee characteristics than discrete Zeners.
What is the minimum cathode current required for regulation in the LM431ACM3?
The LM431ACM3 requires a minimum cathode current (IZ(MIN)) of 1 mA to maintain regulation, as specified in Section 6.5 of the SNVS020H datasheet. Below this threshold, the device exits regulation and output voltage collapses. Designers must size the series resistor (RS) to ensure IZ stays ≥1 mA even at minimum input voltage and maximum load current. This value is consistent across all LM431A-grade devices, including the LM431ACM3.
Does the LM431ACM3 support operation above 70°C ambient?
No - the LM431ACM3 is rated for commercial temperature operation only (0°C to 70°C ambient), as confirmed by its "C" suffix and orderable addendum listing. For extended temperature range (-40°C to 85°C), the LM431AIM3/NOPB (A-grade, industrial temp) or LM431BIM3/NOPB (B-grade) should be selected. Using LM431ACM3 outside its specified range risks parametric shift, increased drift, and potential regulation failure due to unguaranteed performance beyond 70°C.
How does the LM431ACM3 achieve temperature stability?
The LM431ACM3 achieves temperature stability through an internally compensated bandgap reference core and matched transistor geometry, resulting in a guaranteed average temperature coefficient of 50 ppm/°C over 0°C to 70°C. This is implemented in silicon - no external components are needed. The datasheet confirms this stability is ensured across the full operating range, distinguishing it from uncompensated Zener diodes whose voltage drifts significantly with temperature.
LM431ACM3 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:
- 0°C ~ 70°C (TA)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- SOT-23-3
LM431ACM3 FAQ
1.How can I place an order for LM431ACM3 through Aetrix?
Please submit a Request for Quotation (RFQ) for LM431ACM3 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 LM431ACM3 reliable?
The price and inventory of LM431ACM3 are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LM431ACM3 is usually 5 days.
3.What payment methods are accepted for LM431ACM3?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LM431ACM3 transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LM431ACM3?
LM431ACM3 orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LM431ACM3 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 LM431ACM3?
For technical support, including LM431ACM3 datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LM431ACM3 requirements.
6.How does Aetrix verify that LM431ACM3 is sourced from the original manufacturer or authorized distributors?
All LM431ACM3 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 LM431ACM3 meets industry standards.
7.What is the process for return or replacement of LM431ACM3?
All LM431ACM3 units undergo pre-shipment inspection (PSI). If there is an issue with LM431ACM3, 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 LM431ACM3 part is unused and in its original packaging.
Return procedure for LM431ACM3:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
LM431ACM3 Tags
-
TL431AIDBZR
Texas Instruments
-
TL431BQDBZR
Texas Instruments
-
AN431AN-ATRG1
Diodes Incorporated
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LM4040CYM3-2.5-TR
Microchip Technology
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LM4040CYM3-4.1-TR
Microchip Technology
-
LM4040EIM3-2.5/NOPB
Texas Instruments
-
AZ431LBNTR-G1
Diodes Incorporated
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LM4040D20IDBZR
Texas Instruments
-
LM4041DIM3-ADJ/NOPB
Texas Instruments
-
LM4040DIM3X-2.5/NOPB
Texas Instruments
-
LM4040DIM3-2.5/NOPB
Texas Instruments
-
AZ431LANTR-G1
Diodes Incorporated
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