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Texas Instruments LM431ACM3X
- Part No.:
- LM431ACM3X
- Manufacturer:
- Texas Instruments
- Category:
- Voltage Reference
- Package:
- TO-236-3, SC-59, SOT-23-3
- Datasheet:
-
LM431ACM3X.pdf
- Description:
- IC VREF SHUNT ADJ 2.2% SOT23-3
- Quantity:
- Payment:
- Shipping:
Inventory:3,061
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Product details
Overview
LM431ACM3X 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, 0.5 Ω dynamic output impedance, and stable operation from 2.5 V to 36 V output range - used for voltage monitoring, current source circuits, and Zener diode replacement in linear power supplies.
For engineers reviewing the LM431ACM3X datasheet, LM431ACM3X pinout, LM431ACM3X application, or LM431ACM3X equivalent, this page provides verified electrical specs, thermal derating guidance, functional mode distinctions (closed-loop regulation vs. open-loop comparator use), and real-world design constraints including minimum cathode current (1 mA) and maximum operating current (100 mA).
Technical Context
The LM431ACM3X operates as a 3-terminal programmable shunt regulator with internal bandgap reference and transconductance amplifier driving an NPN pass transistor. Its regulation relies on feedback via external resistor divider connected to the Reference pin, enabling precise output voltage setting above 2.5 V.
It supports two functional modes: closed-loop regulation (Reference tied to output via divider, requiring 1–100 mA cathode current) and open-loop comparator mode (Reference driven externally). Thermal hysteresis is characterized at ±0.5 mV after cycling between 0°C and 70°C.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Reference Voltage (VREF) | 2.495 V (typical), ±2.5 mV max deviation at 25°C - sets baseline accuracy for all programmed output voltages |
| Temperature Coefficient | 50 ppm/°C (average) - ensures ≤1.75 mV drift over 0°C to 70°C commercial temp range |
| Dynamic Output Impedance | 0.5 Ω (typical at DC) - enables low-noise, high-stability regulation under varying load conditions |
| Cathode Voltage Range | 2.5 V to 36 V - defines programmable output span using external resistors R1/R2 |
| Minimum Cathode Current | 1 mA - required to maintain regulation; below this, device exits active regulation zone |
| Maximum Cathode Current | 100 mA - absolute limit before thermal shutdown or reliability risk in SOT-23 package |
| Reference Input Current | 2–4 μA (typical) - determines bias error in high-impedance feedback networks |
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 1 = Cathode, Pin 2 = Reference, Pin 3 = Anode.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| Cathode (Pin 1) | Output / Shunt Current Terminal | Connects to regulated output node; sinks current to ground to maintain set voltage - must handle up to 100 mA |
| Reference (Pin 2) | Feedback Input | High-impedance input (2–4 μA) sensing voltage divider output; sets regulation point when VREF = 2.495 V |
| Anode (Pin 3) | Ground Reference | Common return path for internal circuitry; typically connected to system ground - not floating |
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 despite rapid load transients in power supply feedback loops |
| Fast Turn-On Response | Sub-microsecond recovery from dropout - critical for overvoltage protection and crowbar circuits |
| Low-Output Noise | Typical 20 μVRMS (10 Hz–10 kHz) - suitable for precision analog references without added filtering |
| Temperature Compensation | Ensured stability across full 0°C to 70°C range - no external compensation required for commercial applications |
Applications
| Switching Power Supply Feedback | Voltage Monitoring Circuit |
|---|---|
Use Scenario: Secondary-side voltage sensing in isolated flyback converters where optocoupler feedback requires precise reference. IC Role / Device Role / Timing Role: Adjustable shunt regulator providing stable 2.5 V reference to optocoupler LED driver - sets regulation threshold for primary controller. Use Value: Enables ±1% output voltage accuracy over line/load/temperature with minimal external components and no trimming. |
Use Scenario: Overvoltage detection in battery management systems protecting Li-ion cells from >4.3 V. IC Role / Device Role / Timing Role: Precision comparator with programmable trip point - Reference pin biased by resistor divider from monitored rail. Use Value: Delivers 50 ppm/°C trip-point stability, eliminating thermal drift errors common in discrete Zener-based monitors. |
| Current Source/Sink | Zener Diode Replacement |
Use Scenario: Constant-current LED driver for indicator lighting in industrial HMIs with wide input voltage range. IC Role / Device Role / Timing Role: Shunt regulator configured as two-terminal current source - Cathode-Anode path sets current via series resistor. Use Value: Provides 1% current accuracy over 0–70°C without active transistor biasing or op-amp circuitry. |
Use Scenario: Replacing 3.3 V Zener diodes in legacy analog sensor signal conditioning circuits. IC Role / Device Role / Timing Role: Programmable shunt element replacing fixed-voltage Zener - Reference pin grounded, Cathode-Anode used as adjustable breakdown node. Use Value: Eliminates inventory of multiple Zener values; achieves tighter tolerance (±1%) and lower dynamic impedance than standard 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 reference, but 0.2 Ω dynamic impedance and −1.4 mV/V cathode voltage coefficient - tighter spec, higher cost | Preferred in high-accuracy SMPS feedback where <0.5% total output error required | Select TL431ACDBVR when dynamic impedance <0.3 Ω or cathode coefficient <−1.2 mV/V is mandatory |
| AS431ARTDT | 2.5 V reference (±1%), 100 ppm/°C TC, 2 Ω dynamic impedance - wider tolerance, lower performance | Suitable for non-critical voltage clamping or basic overvoltage alarms where cost dominates | Choose AS431ARTDT only for cost-sensitive consumer applications with relaxed accuracy requirements |
Compared with LM431ACM3X, TL431ACDBVR offers superior regulation fidelity at higher unit cost, while AS431ARTDT trades accuracy and stability for lower BOM cost - neither is pin-compatible, requiring layout revision for substitution.
Availability
LM431ACM3X is available at Aetrix Electronics and suitable for switching power supply feedback, voltage monitoring, and current source/sink circuits requiring stable component supply across industrial and commercial temperature ranges.
Supply support for LM431ACM3X 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, designing and manufacturing analog ICs, embedded processors, and digital signal processors for industrial, automotive, and consumer markets.
The LM431 product line delivers precision shunt regulation for cost-sensitive, space-constrained applications - designed specifically to replace discrete Zener diodes while maintaining guaranteed temperature stability and low dynamic impedance.
FAQ
What is the operating temperature range for LM431ACM3X?
The LM431ACM3X is rated for commercial operation from 0°C to 70°C. This range is confirmed in the TI datasheet's Recommended Operating Conditions table and applies specifically to the "C" grade variant denoted in the part number. Operation outside this range may result in unguaranteed reference voltage accuracy or increased thermal hysteresis. The LM431ACM3X does not support industrial (−40°C to 85°C) or extended temperature grades.
Can LM431ACM3X be used as a comparator?
Yes, the LM431ACM3X can operate in open-loop comparator mode per TI's Device Functional Modes section. In this configuration, the Reference pin is driven externally (not via resistor divider), and the Cathode switches between high-impedance and sinking states based on input threshold. However, LM431ACM3X lacks dedicated comparator features like rail-to-rail output or propagation delay specs - it is optimized for regulation, not high-speed comparison.
What is the minimum cathode current required for regulation in LM431ACM3X?
The LM431ACM3X requires a minimum cathode current of 1 mA to maintain regulation, as specified in the Electrical Characteristics table under IZ(MIN). Below this value, the internal amplifier cannot sustain proper biasing, causing output voltage to deviate from the programmed value. This requirement directly impacts series resistor sizing in shunt regulator designs, especially under worst-case low-input/high-load conditions.
How does the dynamic output impedance of LM431ACM3X affect circuit stability?
The LM431ACM3X has a typical dynamic output impedance of 0.5 Ω, which minimizes voltage droop during fast load transients. However, its stability boundary depends heavily on external capacitance - Figure 2 in the datasheet shows oscillation risk zones when output capacitors exceed 10 nF without series resistance. For stable operation, keep CL ≤10 nF or add ≥10 Ω in series with larger capacitors near the Cathode pin.
Is LM431ACM3X RoHS compliant and lead-free?
Yes, the LM431ACM3X/NOPB variant is RoHS compliant and lead-free, with Green (RoHS & no Sb/Br) eco plan and CU SN lead finish, as documented in TI's Package Option Addendum. The base part number LM431ACM3X (without /NOPB suffix) is marked NRND and has TBD eco plan - only LM431ACM3X/NOPB guarantees RoHS compliance and is actively distributed by TI and authorized distributors.
LM431ACM3X 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
LM431ACM3X FAQ
1.How can I place an order for LM431ACM3X through Aetrix?
Please submit a Request for Quotation (RFQ) for LM431ACM3X 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 reliable?
The price and inventory of LM431ACM3X are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LM431ACM3X is usually 5 days.
3.What payment methods are accepted for LM431ACM3X?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LM431ACM3X transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LM431ACM3X?
LM431ACM3X orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LM431ACM3X 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?
For technical support, including LM431ACM3X datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LM431ACM3X requirements.
6.How does Aetrix verify that LM431ACM3X is sourced from the original manufacturer or authorized distributors?
All LM431ACM3X 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 meets industry standards.
7.What is the process for return or replacement of LM431ACM3X?
All LM431ACM3X units undergo pre-shipment inspection (PSI). If there is an issue with LM431ACM3X, 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 part is unused and in its original packaging.
Return procedure for LM431ACM3X:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
LM431ACM3X Tags
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