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Texas Instruments LM431ACMX
- Part No.:
- LM431ACMX
- Manufacturer:
- Texas Instruments
- Category:
- Voltage Reference
- Package:
- 8-SOIC (0.154", 3.90mm Width)
- Datasheet:
-
LM431ACMX.pdf
- Description:
- IC VREF SHUNT ADJ 2.2% 8SOIC
- Quantity:
- Payment:
- Shipping:
Inventory:3,372
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Product details
Overview
LM431ACMX from Texas Instruments is a precision adjustable shunt voltage regulator with 2.495 V reference voltage, ±17 mV reference deviation over temperature, 0.75 Ω dynamic output impedance, and 1–100 mA cathode current range. It operates as a programmable Zener replacement in feedback loops of linear and switching power supplies, voltage monitors, and current sink circuits.
For engineers reviewing the LM431ACMX datasheet, LM431ACMX pinout, LM431ACMX application, or LM431ACMX equivalent, this page delivers verified package mapping (SOIC-8), confirmed thermal performance (RθJA = 126.9 °C/W), exact pin functions per TI's official pin configuration, and two validated alternative parts for commercial-grade shunt regulation use cases.
Technical Context
The LM431ACMX implements a three-terminal bandgap-based shunt regulator architecture with internal error amplifier and NPN pass transistor. Its reference node senses external resistor-divider voltage, enabling precise output programming from 2.5 V to 36 V via R1/R2 ratio.
It operates in closed-loop regulation mode with 1 mA minimum cathode current and supports open-loop comparator operation. Temperature compensation ensures stable 50 ppm/°C average TC across 0°C to 70°C, and its low 0.3–1 μA OFF-state current enables high-impedance monitoring applications.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Reference Voltage (VREF) | 2.495 V (typical at 25°C, 2.47–2.52 V min/max over temp - sets base accuracy of all programmed outputs) |
| Reference Deviation | ±17 mV over full 0°C to 70°C range - defines worst-case output voltage drift without external trimming |
| Cathode Current Range | 1–100 mA - determines usable load current headroom and external series resistor sizing |
| Dynamic Output Impedance | 0.75 Ω (typical) - enables tight regulation under fast load transients when used with proper bypassing |
| Temperature Coefficient | 50 ppm/°C (average) - quantifies long-term stability in thermally varying environments |
| Max Cathode Voltage | 37 V - defines absolute upper limit for input supply or overvoltage protection clamping |
| ESD Rating (HBM) | ±2500 V - indicates robustness during board handling and assembly before soldering |
Pinout & Package
LM431ACMX is housed in an 8-pin SOIC (D package) with 4.90 mm × 3.91 mm body size, RoHS-compliant green finish, and CU SN lead finish. Pin 4 and Pin 5 are internally unconnected (NC).
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| Cathode (Pin 1) | Output / Shunt current path | Main regulated node - connects to supply rail and external series resistor; sinks current to maintain set voltage |
| Reference (Pin 8) | Feedback input | Senses divided output voltage; must be connected to resistor divider midpoint for closed-loop regulation |
| Anode (Pins 2, 3, 6, 7) | Ground return | All four pins tied internally to substrate ground - must be connected to system GND for stable operation |
| NC (Pins 4, 5) | No internal connection | Unused terminals - left floating or grounded per layout best practice; no electrical function |
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 values |
| Low dynamic output impedance | 0.75 Ω typical - maintains regulation accuracy during rapid load changes without external compensation |
| Fast turn-on response | Enables use in transient-sensitive feedback paths and crowbar protection circuits - no startup delay penalty |
| Low-output noise | Minimizes ripple injection into sensitive analog references or control loops - critical in precision ADC/DAC systems |
| Space-saving SOIC-8 package | 4.90 mm × 3.91 mm footprint - supports high-density PCB layouts while retaining thermal margin (0.81 W dissipation) |
Applications
| Switch-Mode Power Supply Feedback | Voltage Monitoring Circuit |
|---|---|
Use Scenario: Secondary-side voltage sensing in isolated flyback or forward converters. IC Role / Device Role / Timing Role: Shunt regulator providing optocoupler bias and precise error signal to primary controller. Use Value: Enables ±1% output regulation across line/load/temperature with minimal external components and no secondary-side LDO. |
Use Scenario: Overvoltage detection on 12 V automotive or industrial bus lines. IC Role / Device Role / Timing Role: Precision threshold comparator triggering shutdown or alarm when bus exceeds 12.5 V. Use Value: Replaces discrete Zener + transistor circuit with single IC offering tighter tolerance (±0.5%) and lower quiescent current (≤4 μA). |
| Current Sink for LED Bias | Zener Diode Replacement |
Use Scenario: Constant-current drive for indicator LEDs in instrumentation front panels. IC Role / Device Role / Timing Role: Adjustable shunt element setting LED current via R1/R2 network and sense resistor. Use Value: Delivers stable 5–20 mA sink current independent of supply variation (15–30 V), eliminating thermal runaway risk of basic Zeners. |
Use Scenario: Reference generation in analog sensor signal conditioning stages. IC Role / Device Role / Timing Role: Precision 2.5 V reference replacing 5% tolerance 2.4 V Zener diode. Use Value: Improves ADC measurement accuracy by reducing reference drift from 100 ppm/°C to 50 ppm/°C and lowering output impedance by 10×. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar shunt regulator applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| TL431ACDR | Same 2.495 V reference, but 0.2 Ω lower dynamic impedance (0.55 Ω typ); wider -40°C to 125°C temp range | Preferred in automotive or extended-temp industrial designs requiring higher reliability margin | Select TL431ACDR when operating above 70°C or when <0.6 Ω rZ is required for ultra-stable feedback |
| LM431CIMX/NOPB | Identical SOIC-8 package and pinout; tighter 2.485–2.51 V VREF tolerance (±10 mV vs ±17 mV), rated for -40°C to 85°C | Suitable for industrial systems needing improved initial accuracy and broader temperature coverage | Choose LM431CIMX/NOPB where ±0.4% reference accuracy is mandatory and ambient exceeds 70°C |
Compared with LM431ACMX, TL431ACDR offers superior thermal range and dynamic impedance for demanding environments, while LM431CIMX/NOPB provides tighter factory calibration and extended low-temperature operation - both retain identical SOIC-8 layout compatibility but differ in accuracy grade and qualification scope.
Availability
LM431ACMX is available at Aetrix Electronics and suitable for switch-mode power supply feedback, voltage monitoring, current sink circuits, and Zener diode replacements requiring stable component supply across commercial temperature range (0°C to 70°C).
Supply support for LM431ACMX 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 headquartered in Dallas, Texas, delivering analog and embedded processing solutions for industrial, automotive, and personal electronics markets.
The LM431ACMX belongs to TI's precision shunt regulator product line, engineered for high-accuracy voltage reference and programmable regulation in cost-sensitive, space-constrained power management applications.
FAQ
What is the maximum cathode voltage rating for LM431ACMX?
The LM431ACMX has an absolute maximum cathode voltage rating of 37 V. Exceeding this value risks permanent device damage. In normal operation, the cathode voltage should remain ≤36 V to ensure reliable regulation and avoid overstress conditions specified in the Absolute Maximum Ratings table of the TI datasheet SNVS020H.
Does LM431ACMX require an external capacitor for stability?
No, LM431ACMX does not require an external capacitor for basic regulation stability. However, TI recommends adding a 0.1 µF ceramic bypass capacitor close to the cathode pin when noise immunity is critical. The device remains stable without it across its full 1–100 mA operating range, as confirmed in Figure 2 (Stability Boundary Conditions) of the LM431 datasheet.
How is the output voltage calculated for LM431ACMX?
The output voltage (VO) of LM431ACMX is calculated using VO = VREF × (1 + R1/R2), where VREF = 2.495 V (typical), R1 connects between cathode and reference pin, and R2 connects between reference pin and ground. For example, R1 = R2 = 1 kΩ yields VO ≈ 5.0 V. Equation 6 in the TI datasheet confirms this relationship.
What is the minimum cathode current needed for regulation in LM431ACMX?
The LM431ACMX requires a minimum cathode current (IZ(MIN)) of 0.4 mA (typical) and 1 mA (guaranteed) to maintain regulation. Below 1 mA, the device may exit regulation and exhibit increased output impedance or voltage error. This value is specified in Section 6.5 Electrical Characteristics of the SNVS020H datasheet.
Is LM431ACMX pin-compatible with other LM431 variants in SOIC-8?
Yes, LM431ACMX is pin-compatible with all SOIC-8 packaged LM431 variants (e.g., LM431AIMX/NOPB, LM431BCM/NOPB) because they share identical D-package pinout, terminal assignments, and NC pin locations. The only differences lie in reference voltage tolerance (A/B/C grade) and temperature range (commercial vs. industrial), not physical connectivity.
LM431ACMX Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Texas Instruments
- Package/Case:
- 8-SOIC (0.154", 3.90mm Width)
- 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:
- 8-SOIC
LM431ACMX FAQ
1.How can I place an order for LM431ACMX through Aetrix?
Please submit a Request for Quotation (RFQ) for LM431ACMX 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 LM431ACMX reliable?
The price and inventory of LM431ACMX are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LM431ACMX is usually 5 days.
3.What payment methods are accepted for LM431ACMX?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LM431ACMX transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LM431ACMX?
LM431ACMX orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LM431ACMX 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 LM431ACMX?
For technical support, including LM431ACMX datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LM431ACMX requirements.
6.How does Aetrix verify that LM431ACMX is sourced from the original manufacturer or authorized distributors?
All LM431ACMX 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 LM431ACMX meets industry standards.
7.What is the process for return or replacement of LM431ACMX?
All LM431ACMX units undergo pre-shipment inspection (PSI). If there is an issue with LM431ACMX, 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 LM431ACMX part is unused and in its original packaging.
Return procedure for LM431ACMX:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
LM431ACMX Tags
-
TL431AIDBZR
Texas Instruments
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TL431BQDBZR
Texas Instruments
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AN431AN-ATRG1
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LM4040CYM3-2.5-TR
Microchip Technology
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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
Texas Instruments
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LM4041DIM3-ADJ/NOPB
Texas Instruments
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LM4040DIM3X-2.5/NOPB
Texas Instruments
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LM4040DIM3-2.5/NOPB
Texas Instruments
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AZ431LANTR-G1
Diodes Incorporated
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