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Texas Instruments LM431ACM3X/NOPB
- Part No.:
- LM431ACM3X/NOPB
- Manufacturer:
- Texas Instruments
- Category:
- Voltage Reference
- Package:
- TO-236-3, SC-59, SOT-23-3
- Datasheet:
-
LM431ACM3X/NOPB.pdf
- Description:
- IC VREF SHUNT ADJ 2.2% SOT23-3
- Quantity:
- Payment:
- Shipping:
Inventory:82,151
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Product details
Overview
LM431ACM3X/NOPB from Texas Instruments is a precision adjustable shunt regulator in SOT-23-3 package, featuring 2.495 V nominal reference voltage (VREF), ±17 mV max reference deviation over temperature, 0.5 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 isolated DC/DC converters and voltage monitors.
For engineers reviewing the LM431ACM3X/NOPB datasheet, LM431ACM3X/NOPB pinout, LM431ACM3X/NOPB application, or LM431ACM3X/NOPB equivalent, key selection criteria include reference accuracy across 0°C to 70°C, low dynamic impedance for stable loop response, SOT-23 footprint compatibility with space-constrained PCBs, and guaranteed turn-on behavior for Zener replacement in linear regulators and overvoltage protection circuits.
Technical Context
The LM431ACM3X/NOPB implements a bandgap-based reference core with internal error amplifier and NPN pass transistor, enabling precise shunt regulation via external resistor divider on the REF pin. Its architecture supports both closed-loop voltage regulation (with feedback from cathode to REF) and open-loop comparator mode (with REF driven externally).
It operates with 2.5 V to 36 V programmable output range, maintains regulation with cathode current from 1 mA to 100 mA, and delivers thermal stability via on-chip temperature compensation - evidenced by 50 ppm/°C average temperature coefficient and ≤17 mV VREF drift over full commercial temperature range.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| VREF (25°C) | 2.495 V typical; sets base accuracy for programmable output voltage via R1/R2 divider |
| VREF Deviation | ±17 mV max over 0°C to 70°C; defines worst-case output voltage tolerance in temperature-varying environments |
| rZ (Dynamic Impedance) | 0.5 Ω typical at 0 Hz; ensures minimal output voltage perturbation under fast load transients |
| IZ(MIN) | 1 mA minimum cathode current; determines smallest usable series resistor for reliable regulation start-up |
| Cathode Voltage Range | 2.5 V to 36 V; enables direct replacement of discrete Zener diodes up to 36 V systems |
| Reference Input Current | 2–4 μA typical; allows high-value feedback resistors (>1 MΩ) without significant divider error |
| ESD Rating (HBM) | ±2500 V; meets standard handling requirements for automated assembly without special ESD controls |
Pinout & Package
SOT-23-3 package (2.92 mm × 1.30 mm body size), surface-mount, tape-and-reel (3000 pcs/reel), RoHS-compliant with Sn lead finish and MSL Level-1 rating.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| Cathode (Pin 1) | Output / Shunt current path | Connects to regulated voltage node; sinks current to ground to maintain set voltage |
| Reference (Pin 2) | Feedback input | High-impedance node sensing divided output voltage; sets regulation point via external resistor network |
| Anode (Pin 3) | Ground reference | Typically connected to system ground; completes shunt current path through internal transistor |
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 |
| Temperature-compensated reference | 50 ppm/°C average TC and ≤17 mV VREF drift over 0°C–70°C - enables stable performance in ambient-varying applications |
| Fast turn-on response | Sharp knee characteristic enables rapid transition into regulation - critical for crowbar and overvoltage shutdown circuits |
| Low-output noise | Minimal broadband noise contribution (<10 µV RMS typical) preserves signal integrity in precision analog feedback paths |
| Low-dynamic output impedance | 0.5 Ω typical rZ ensures <5 mV output shift under 10 mA load step - improves transient regulation in switching supplies |
Applications
| Isolated Flyback Feedback | Voltage Monitor Circuit |
|---|---|
Use Scenario: Secondary-side voltage sensing in AC/DC flyback converters with optocoupler feedback. IC Role / Device Role / Timing Role: Precision shunt regulator providing stable 2.5 V reference to drive optocoupler LED, enabling accurate primary-side regulation. Use Value: Maintains ±1% output voltage accuracy across line/load/temperature while occupying <1.5 mm² PCB area in SOT-23. |
Use Scenario: Detecting overvoltage condition on a 12 V automotive rail before downstream IC damage occurs. IC Role / Device Role / Timing Role: Adjustable threshold comparator with hysteresis, triggering MOSFET gate shutdown when VIN exceeds 13.2 V. Use Value: Replaces dual op-amp + reference solution with single 3-pin device, reducing BOM count and layout complexity. |
| Current Sink for LED Bias | Zener Diode Replacement |
Use Scenario: Constant-current bias for high-brightness indicator LEDs in industrial HMIs. IC Role / Device Role / Timing Role: Shunt regulator configured as precision current sink, delivering 20 mA ±2% independent of supply variation from 5 V to 24 V. Use Value: Eliminates thermal drift issues of discrete transistor+resistor current sources; achieves <0.5% current stability over temperature. |
Use Scenario: Replacing 3.3 V, 5.1 V, and 12 V Zener diodes in legacy power supply designs. IC Role / Device Role / Timing Role: Single-component, pin-compatible upgrade offering tighter tolerance (±0.5% vs ±5%), lower impedance, and guaranteed tempco. Use Value: Enables drop-in reliability improvement without PCB redesign - same SOT-23 footprint and cathode/anode/ref pinout as discrete Zeners. |
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 2.495 V VREF, but 0.2 Ω typical rZ and −2.5 mV/V ΔVREF/ΔVZ vs −1.4 mV/V for LM431ACM3X/NOPB | Better dynamic regulation in high-frequency SMPS; slightly higher cost and different SOT-23 marking (TL431 vs LM431) | Select TL431ACDBVR when loop bandwidth >500 kHz or cathode voltage >20 V dominates design priorities |
| AS431ARTDT-13 | 2.5 V VREF, ±25 mV VREF deviation over 0°C–70°C, 1.2 Ω rZ, and 2.5 μA IREF - looser initial accuracy and higher impedance | Lower-cost option for non-critical biasing or monitoring where ±2% output tolerance is acceptable | Choose AS431ARTDT-13 only for cost-sensitive consumer applications where thermal drift and transient response are secondary |
Compared with TL431ACDBVR and AS431ARTDT-13, the LM431ACM3X/NOPB offers the best balance of reference accuracy (±0.7% typical), low dynamic impedance (0.5 Ω), and proven stability in legacy flyback feedback designs - making it ideal for industrial power supplies requiring long-term calibration retention and minimal layout changes.
Availability
LM431ACM3X/NOPB is available at Aetrix Electronics and suitable for isolated DC/DC converters, voltage monitoring systems, and precision current sink circuits requiring stable component supply with consistent SOT-23-3 packaging and commercial-grade temperature performance.
Supply support for LM431ACM3X/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 company headquartered in Dallas, Texas, specializing in analog, embedded processing, and power management ICs for industrial, automotive, and communications markets.
The LM431 product line delivers precision shunt regulation for feedback control in power conversion and voltage supervision - designed specifically for engineers needing Zener-grade simplicity with IC-grade accuracy and thermal stability.
FAQ
What is the reference voltage tolerance of LM431ACM3X/NOPB over temperature?
The LM431ACM3X/NOPB has a reference voltage (VREF) of 2.495 V typical at 25°C, with maximum deviation of ±17 mV over the full 0°C to 70°C operating range. This corresponds to ±0.68% total error, including initial tolerance and thermal drift - verified per Electrical Characteristics Table 6.5 in the SNVS020H datasheet.
Can LM431ACM3X/NOPB replace a standard 3.3 V Zener diode directly?
Yes, the LM431ACM3X/NOPB can directly replace a 3.3 V Zener diode using a two-resistor divider: set R1 = 3.2 kΩ and R2 = 10 kΩ to achieve 3.3 V output (VO = VREF × (1 + R1/R2)). Unlike discrete Zeners, it guarantees 50 ppm/°C tempco and 0.5 Ω dynamic impedance - improving regulation accuracy and transient response without PCB layout changes.
What is the minimum cathode current required for regulation in LM431ACM3X/NOPB?
The LM431ACM3X/NOPB 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 - so the series resistor must be sized to ensure ≥1 mA even at lowest input voltage and highest load current.
Does LM431ACM3X/NOPB support operation above 36 V cathode voltage?
No, the absolute maximum cathode voltage for LM431ACM3X/NOPB is 37 V (Section 6.1), and recommended operating maximum is 36 V. Exceeding 36 V risks permanent damage or parametric shift. For >36 V applications, use external clamping (e.g., TVS diode) or select a high-voltage shunt regulator like TL432BIDBZR with 40 V rating.
How does the LM431ACM3X/NOPB pinout compare to TO-92 and SOIC variants?
The LM431ACM3X/NOPB uses SOT-23-3 pinout: Pin 1 = Cathode, Pin 2 = Reference, Pin 3 = Anode. This matches the pin assignment of LM431ACZ (TO-92) and LM431ACM (SOIC-8 pins 1,2,3), ensuring identical circuit integration across packages - no schematic or layout rework needed when migrating between footprints.
LM431ACM3X/NOPB 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:
- 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:
- SOT-23-3
LM431ACM3X/NOPB FAQ
1.How can I place an order for LM431ACM3X/NOPB through Aetrix?
Please submit a Request for Quotation (RFQ) for LM431ACM3X/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 LM431ACM3X/NOPB reliable?
The price and inventory of LM431ACM3X/NOPB are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LM431ACM3X/NOPB is usually 5 days.
3.What payment methods are accepted for LM431ACM3X/NOPB?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LM431ACM3X/NOPB transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LM431ACM3X/NOPB?
LM431ACM3X/NOPB orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LM431ACM3X/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 LM431ACM3X/NOPB?
For technical support, including LM431ACM3X/NOPB datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LM431ACM3X/NOPB requirements.
6.How does Aetrix verify that LM431ACM3X/NOPB is sourced from the original manufacturer or authorized distributors?
All LM431ACM3X/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 LM431ACM3X/NOPB meets industry standards.
7.What is the process for return or replacement of LM431ACM3X/NOPB?
All LM431ACM3X/NOPB units undergo pre-shipment inspection (PSI). If there is an issue with LM431ACM3X/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 LM431ACM3X/NOPB part is unused and in its original packaging.
Return procedure for LM431ACM3X/NOPB:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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