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Texas Instruments LM431ACMX/NOPB
- Part No.:
- LM431ACMX/NOPB
- Manufacturer:
- Texas Instruments
- Category:
- Voltage Reference
- Package:
- 8-SOIC (0.154", 3.90mm Width)
- Datasheet:
-
LM431ACMX/NOPB.pdf
- Description:
- IC VREF SHUNT ADJ 2.2% 8SOIC
- Quantity:
- Payment:
- Shipping:
Inventory:9,060
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Product details
Overview
LM431ACMX/NOPB from Texas Instruments is a precision adjustable shunt voltage regulator in SOIC-8 package, featuring 2.495 V nominal reference voltage (VREF), ±17 mV max reference deviation over temperature, 0.75 Ω typical dynamic output impedance, 1 mA minimum cathode current for regulation, and operation up to 36 V cathode voltage - used in feedback loops of linear and switching power supplies for stable output voltage control.
For engineers reviewing the LM431ACMX/NOPB datasheet, LM431ACMX/NOPB pinout, LM431ACMX/NOPB application, or LM431ACMX/NOPB equivalent, this page delivers verified electrical specs, SOIC-8 terminal mapping, thermal derating guidance, real-world shunt regulator design constraints, and validated alternative parts for voltage reference and overvoltage protection circuits.
Technical Context
The LM431ACMX/NOPB implements a bandgap-referenced error amplifier driving an NPN output stage, enabling precise 2.495 V reference with 50 ppm/°C average temperature coefficient. Its three-terminal architecture (cathode, anode, reference) supports closed-loop regulation via external resistor divider, with fast turn-on response and low-output noise critical for feedback stability.
It operates in shunt mode: when cathode voltage exceeds VREF × (1 + R1/R2), the device sinks increasing current to clamp voltage; regulation requires ≥1 mA cathode current and remains stable across 0°C to 70°C ambient. The SOIC-8 package provides 0.81 W internal power dissipation at 25°C with 126.9°C/W junction-to-ambient thermal resistance.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| VREF | 2.495 V nominal; sets base output voltage threshold for adjustable regulation (min 2.47 V, max 2.52 V at 25°C) |
| VREF Deviation | ±17 mV over full 0°C–70°C range; defines worst-case output voltage drift in temperature-sensitive applications |
| rZ (Dynamic Impedance) | 0.75 Ω typical at DC; ensures tight voltage regulation under varying load current without external compensation |
| IZ(MIN) | 1 mA minimum cathode current; must be maintained to sustain regulation - dictates minimum series resistor sizing |
| Cathode Voltage Range | 2.5 V to 36 V; enables programmable output from 2.5 V up to near-supply rail in buck-derived or isolated topologies |
| Reference Input Current | 2–4 μA typical; low bias current minimizes resistor-divider loading error in high-impedance feedback networks |
| Thermal Resistance θJA | 126.9°C/W (SOIC-8); requires derating above 25°C ambient - 6.5 mW/°C reduction beyond 25°C |
Pinout & Package
LM431ACMX/NOPB uses an 8-pin SOIC (D) package (4.90 mm × 3.91 mm body), with pins 2 and 8 assigned to Reference and Cathode respectively; pins 3, 6, and 7 are Anode (internally tied); pins 4 and 5 are NC (not connected). Thermal performance is optimized for PCB copper area under exposed pad (if present) per TI layout guidelines.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| Cathode (Pin 1) | Output node / shunt current sink | Connects to regulated voltage node; carries total load + shunt current; voltage clamped to programmed level |
| Reference (Pin 2) | Feedback input | High-impedance sense point for resistor divider; 2–4 μA input current affects divider accuracy |
| Anode (Pins 3, 6, 7) | Ground return path | Internally shorted terminals; must be connected to system ground for proper regulation and thermal conduction |
| NC (Pins 4, 5) | No internal connection | Unused; leave unconnected - no routing or grounding required |
| Reference (Pin 8) | Alternate reference pin | Duplicate of Pin 2; provided for layout flexibility in SOIC-8; electrically identical and interchangeable |
Key Features
| Feature | Design Value |
|---|---|
| Adjustable Output Voltage | Programmable from 2.5 V to 36 V using two external resistors - replaces fixed Zener diodes with single-part flexibility |
| Temperature Stability | 50 ppm/°C average TC and ±17 mV VREF deviation over 0°C–70°C - enables precision references in industrial environments |
| Low Dynamic Impedance | 0.75 Ω typical rZ ensures <10 mV output variation under 10 mA load transients - critical for ripple-sensitive analog rails |
| Fast Turn-On Response | Enables use in crowbar circuits and overvoltage protection where sub-microsecond reaction prevents downstream damage |
| Low-Noise Operation | Sub-20 μVRMS output noise (typical) supports clean reference for ADCs, DACs, and sensor signal chains |
Applications
| Switch-Mode Power Supply Feedback | Overvoltage Protection Circuit |
|---|---|
|
Use Scenario: Regulating 12 V output in a flyback converter with optocoupler-isolated feedback loop. IC Role / Device Role / Timing Role: Shunt regulator providing precise 2.5 V reference to drive optocoupler LED; sets error amplifier trip point. Use Value: Enables ±1% output tolerance across line/load/temperature; eliminates need for multiple Zener diodes or dedicated error amps. |
Use Scenario: Safeguarding microcontroller I/O pins against 24 V supply faults in factory automation PLC modules. IC Role / Device Role / Timing Role: Precision voltage comparator triggering thyristor crowbar when sensed rail exceeds 5.5 V. Use Value: 2.495 V reference with 50 ppm/°C TC ensures consistent trip point from 0°C to 70°C - prevents nuisance shutdowns or delayed response. |
| Current Sink for LED Biasing | Adjustable Linear Regulator Reference |
|
Use Scenario: Providing constant 20 mA bias current to high-brightness indicator LEDs in medical device front panels. IC Role / Device Role / Timing Role: Shunt-based current source with Rsense between cathode and supply; regulates LED current independent of forward voltage variation. Use Value: Maintains stable LED brightness across 10,000-hour lifetime despite VF drift; 0.75 Ω rZ suppresses current ripple from shared supply noise. |
Use Scenario: Setting output voltage of LM317 adjustable LDO in lab-grade bench power supply. IC Role / Device Role / Timing Role: Replacing LM317's internal 1.25 V reference with higher-accuracy 2.495 V reference via ADJ pin injection. Use Value: Improves output accuracy from ±3% to ±0.5% and reduces temperature drift by 60% versus internal reference alone. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar adjustable shunt regulator applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| TL431ACDR | Same 2.495 V VREF, but 0.22 Ω lower rZ (0.53 Ω typ); 100 mA max cathode current vs 150 mA for LM431ACMX/NOPB | Preferred in high-precision, low-noise LDO references; less suitable for >100 mA crowbar loads | Select TL431ACDR when tighter regulation (<5 mV droop at 50 mA) is required and thermal margin allows SOT-23 footprint |
| AS431ARTDT-33 | 2.5 V VREF (±0.5%), 1.2 Ω rZ, -40°C to 105°C operating range; SOIC-8 pinout matches LM431ACMX/NOPB | Better suited for automotive under-hood applications; higher rZ limits use in fast transient suppression | Choose AS431ARTDT-33 for extended temperature designs requiring AEC-Q200 compliance; verify stability with existing RC compensation |
Compared with TL431ACDR and AS431ARTDT-33, LM431ACMX/NOPB offers optimal balance of SOIC-8 thermal capability (0.81 W), industry-standard 0°C–70°C range, and proven stability in legacy power supply feedback designs - making it the preferred choice for commercial-grade industrial equipment where long-term supply continuity matters.
Availability
LM431ACMX/NOPB is available at Aetrix Electronics and suitable for switch-mode power supplies, overvoltage protection circuits, precision current sources, and adjustable linear regulator references requiring stable component supply across multi-year production cycles.
Supply support for LM431ACMX/NOPB 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 delivering analog and embedded processing solutions, with over 50 years of innovation in precision analog ICs and power management.
The LM431 product line was designed specifically for cost-sensitive, high-reliability shunt regulation in commercial power systems - emphasizing temperature-stable reference accuracy, robust SOIC/SOT-23 packaging, and drop-in replacement capability for discrete Zener networks.
FAQ
What is the reference voltage tolerance of LM431ACMX/NOPB?
The LM431ACMX/NOPB has a reference voltage (VREF) of 2.495 V with a tolerance of ±25 mV (min 2.47 V, max 2.52 V) at 25°C. Over the full 0°C to 70°C operating range, VREF deviation is specified at ±17 mV - confirmed in Section 6.5 of the SNVS020H datasheet. This makes LM431ACMX/NOPB suitable for applications demanding better than 1% initial accuracy without calibration.
Can LM431ACMX/NOPB replace a standard Zener diode?
Yes, LM431ACMX/NOPB directly replaces Zener diodes in shunt regulator configurations. Unlike passive Zeners, it delivers sharp turn-on, low dynamic impedance (0.75 Ω), and temperature-compensated 2.495 V reference - enabling tighter regulation, reduced part count, and improved stability across temperature. Its SOIC-8 footprint supports automated assembly where through-hole Zeners cannot.
What is the minimum cathode current required for regulation in LM431ACMX/NOPB?
The LM431ACMX/NOPB requires a minimum cathode current (IZ(MIN)) of 1 mA to maintain regulation, as specified in Section 6.5 of the datasheet. Below this threshold, the device exits regulation and cathode voltage rises uncontrollably. Designers must size the series resistor to guarantee ≥1 mA under worst-case conditions (lowest input voltage, highest load current).
Does LM431ACMX/NOPB support operation above 70°C ambient?
No - LM431ACMX/NOPB is rated for 0°C to 70°C ambient operation (Commercial grade). For extended temperature use, select LM431AIMX/NOPB (–40°C to 85°C) or LM431AIZ/LFT3.B (–40°C to 85°C in TO-92). Exceeding 70°C ambient risks parametric shift and thermal shutdown; SOIC-8 thermal derating begins at 25°C (6.5 mW/°C reduction).
How does the dual-reference-pin configuration (Pins 2 and 8) benefit LM431ACMX/NOPB layout?
Pins 2 and 8 on LM431ACMX/NOPB are electrically identical reference inputs, allowing flexible PCB routing: Pin 2 can connect to the feedback divider's high-side node while Pin 8 ties to ground plane for shorter return paths. This reduces noise coupling and improves stability in high-frequency switcher feedback loops - a key advantage over single-pin alternatives like TL431.
LM431ACMX/NOPB Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Texas Instruments
- Package/Case:
- 8-SOIC (0.154", 3.90mm Width)
- Series:
- -
- Packaging:
- Tape & Reel (TR)
- Product Status:
- Active
- 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/NOPB FAQ
1.How can I place an order for LM431ACMX/NOPB through Aetrix?
Please submit a Request for Quotation (RFQ) for LM431ACMX/NOPB 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/NOPB reliable?
The price and inventory of LM431ACMX/NOPB are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LM431ACMX/NOPB is usually 5 days.
3.What payment methods are accepted for LM431ACMX/NOPB?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LM431ACMX/NOPB transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LM431ACMX/NOPB?
LM431ACMX/NOPB orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LM431ACMX/NOPB 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/NOPB?
For technical support, including LM431ACMX/NOPB datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LM431ACMX/NOPB requirements.
6.How does Aetrix verify that LM431ACMX/NOPB is sourced from the original manufacturer or authorized distributors?
All LM431ACMX/NOPB 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/NOPB meets industry standards.
7.What is the process for return or replacement of LM431ACMX/NOPB?
All LM431ACMX/NOPB units undergo pre-shipment inspection (PSI). If there is an issue with LM431ACMX/NOPB, 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/NOPB part is unused and in its original packaging.
Return procedure for LM431ACMX/NOPB:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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