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Texas Instruments LM431BCM
- Part No.:
- LM431BCM
- Manufacturer:
- Texas Instruments
- Category:
- Voltage Reference
- Package:
- 8-SOIC (0.154", 3.90mm Width)
- Datasheet:
-
LM431BCM.pdf
- Description:
- IC VREF SHUNT ADJ 1% 8SOIC
- Quantity:
- Payment:
- Shipping:
Inventory:3,867
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Product details
Overview
LM431BCM from Texas Instruments is a precision adjustable shunt regulator IC used as a programmable Zener replacement in voltage reference, overvoltage protection, and current-sink circuits. It delivers 2.5 V reference voltage (±10 mV tolerance), operates from 2.5 V to 36 V output range, supports 1–100 mA cathode current, and maintains 50 ppm/°C average temperature coefficient across 0°C to 70°C.
For engineers reviewing the LM431BCM datasheet, LM431BCM pinout, LM431BCM application, or LM431BCM equivalent, this page provides verified package mapping (SOIC-8), confirmed pin functions (Cathode, Anode, Reference), thermal derating data, dynamic impedance (0.5 Ω typ), and validated alternative options for linear regulation and voltage monitoring designs.
Technical Context
The LM431BCM implements a bandgap-based reference core with internal error amplifier and NPN pass transistor, enabling precise shunt regulation via external resistor divider feedback. Its closed-loop operation requires only two resistors to set output voltage from 2.5 V to 36 V, with minimum cathode current of 1 mA for stable regulation.
It operates in either shunt regulator mode (feedback tied to output) or open-loop comparator mode (reference driven externally), supporting fast turnon response and low-output noise. The SOIC-8 package provides thermal resistance of 126.9°C/W (junction-to-ambient) and supports industrial-grade reliability under recommended operating conditions.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Reference voltage (VREF) | 2.50 V ±10 mV at 10 mA - sets base accuracy for all programmable outputs |
| Output voltage range | 2.5 V to 36 V - programmable via external R1/R2 divider without internal scaling limits |
| Cathode current range | 1 mA to 100 mA - defines minimum bias and maximum shunt capability for load regulation |
| Average tempco | 50 ppm/°C - ensures ≤3.5 mV drift over 0°C–70°C ambient for stable reference performance |
| Dynamic output impedance | 0.5 Ω typical - enables tight regulation under dynamic load transients up to 100 kHz |
| Reference input current | 2–4 μA - determines high-impedance feedback network design and leakage sensitivity |
| ESD rating (HBM) | ±2500 V - confirms robustness during PCB handling and assembly without special ESD controls |
Pinout & Package
LM431BCM is housed in an 8-pin SOIC (D package) with 4.90 mm × 3.91 mm body size, RoHS-compliant green finish (CU SN), and moisture sensitivity level 1 (260°C peak reflow). Pin 1 is Cathode; Pins 2 and 8 are Reference and Anode respectively; Pins 3, 4, 5, 6, 7 are internally unconnected (NC) or Anode ties per TI's functional pin mapping.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| Cathode (Pin 1) | Shunt output node | Primary current path; connects to regulated output rail and series resistor; sinks up to 100 mA |
| Reference (Pin 2) | Feedback input | High-impedance node sensing divided output voltage; drives internal error amplifier |
| Anode (Pin 8) | Ground return | Low-impedance common return for cathode current and reference bias; must be low-noise ground |
| NC (Pins 3, 4, 5, 6, 7) | No internal connection | Unused pins; electrically isolated; may be left floating or grounded per layout best practice |
Key Features
| Feature | Design Value |
|---|---|
| Programmable output voltage | Set precisely from 2.5 V to 36 V using only two external resistors - eliminates need for multiple fixed Zeners |
| Temperature-compensated reference | Stable 2.5 V reference over full 0°C–70°C range with 50 ppm/°C avg. tempco - enables reliable operation in commercial environments |
| Low dynamic output impedance | 0.5 Ω typical - maintains tight output regulation during rapid load changes in power supply feedback loops |
| Fast turnon response | Enables use in crowbar and overvoltage shutdown circuits where sub-microsecond reaction is required |
| Space-saving SOIC-8 package | 4.90 mm × 3.91 mm footprint - supports high-density PCB layouts while providing better thermal dissipation than SOT-23 |
Applications
| Adjustable Linear Power Supply | Voltage Monitoring & Protection |
|---|---|
Use Scenario: Regulating 5 V output from variable 12 V–24 V input in industrial control modules. IC Role / Device Role / Timing Role: Shunt regulator providing precision feedback to three-terminal LDO or discrete pass transistor. Use Value: Enables single-component programmability across multiple output voltages without changing reference ICs or layout. |
Use Scenario: Detecting overvoltage on 12 V automotive battery rail to trigger shutdown before damage occurs. IC Role / Device Role / Timing Role: Precision threshold detector comparing sensed voltage against 12.5 V setpoint via resistor divider. Use Value: Achieves ±0.5% trip accuracy over temperature, outperforming discrete Zener + comparator solutions. |
| Current Sink / Source Circuit | Zener Diode Replacement |
Use Scenario: Driving constant 20 mA LED string in signage applications with wide input voltage variation. IC Role / Device Role / Timing Role: Adjustable current sink using LM431BCM as reference-controlled shunt with external sense resistor. Use Value: Delivers stable current independent of input voltage swings from 15 V to 30 V, reducing thermal drift vs. standard Zener-based sinks. |
Use Scenario: Replacing 3.3 V Zener diode in microcontroller reset circuit requiring tighter tolerance and lower leakage. IC Role / Device Role / Timing Role: Precision shunt reference replacing passive Zener with superior tempco and dynamic impedance. Use Value: Reduces reference error from ±5% to ±0.4% and cuts leakage current by >90% versus 3.3 V Zener diodes. |
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 2.5 V reference, but ±1% initial tolerance (vs. LM431BCM's ±0.4%) and higher 2.0 μA max reference current | Less precise for high-accuracy references; suitable where cost sensitivity outweighs 0.6% VREF error | Select TL431ACDR when budget constraints dominate and ±1% output tolerance is acceptable |
| LM431BIM/NOPB | Identical electrical specs but rated for –40°C to +85°C industrial temperature range (vs. LM431BCM's 0°C–70°C) | Required for extended-temperature deployments such as outdoor power supplies or motor drives | Choose LM431BIM/NOPB when operation below 0°C or above 70°C is mandatory |
Compared with TL431ACDR and LM431BIM/NOPB, the LM431BCM offers the tightest reference tolerance (±0.4%) in the commercial temperature grade, making it optimal for cost-sensitive yet accuracy-critical applications like consumer power adapters and embedded voltage monitors where ambient stays within 0°C–70°C.
Availability
LM431BCM is available at Aetrix Electronics and suitable for adjustable voltage regulation, overvoltage protection, and precision current sink applications requiring stable component supply across industrial, consumer, and automotive electronics programs.
Supply support for LM431BCM 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 specializing in analog and embedded processing technologies, with leadership in power management, signal chain, and precision analog ICs.
The LM431BCM belongs to TI's precision shunt regulator product line, designed specifically for high-accuracy, low-drift voltage reference and programmable regulation in space-constrained commercial applications.
FAQ
What is the reference voltage tolerance of the LM431BCM?
The LM431BCM has a reference voltage (VREF) of 2.50 V with a tolerance of ±10 mV (±0.4%) at 10 mA test current and 25°C, as specified in the Electrical Characteristics table. This tight tolerance enables high-accuracy programmable outputs across its 2.5 V–36 V range. The LM431BCM datasheet confirms this value applies to the BCM grade under commercial temperature conditions (0°C to 70°C).
Can the LM431BCM replace a standard Zener diode directly?
Yes, the LM431BCM can directly replace many Zener diodes in shunt regulator and voltage reference roles, but requires two external resistors to set the output voltage - unlike a fixed Zener. Its advantages include superior temperature stability (50 ppm/°C), lower dynamic impedance (0.5 Ω), and programmability from 2.5 V to 36 V. For example, a 5.1 V Zener replacement uses R1 = R2 = 1 kΩ to achieve VO = 2.5 × (1 + 1) = 5.0 V with far better accuracy and drift performance than discrete Zeners.
What is the minimum cathode current required for regulation in the LM431BCM?
The LM431BCM requires a minimum cathode current (IZ(MIN)) of 1 mA to maintain regulation, as specified in the Electrical Characteristics table. Below this threshold, the device exits regulation and output voltage becomes unstable. Designers must ensure the series resistor (RS) supplies ≥1 mA even at worst-case conditions: lowest input voltage and highest load current. This value is consistent across all LM431 variants including the LM431BCM.
Does the LM431BCM support operation beyond 36 V output?
No, the LM431BCM absolute maximum cathode voltage is 37 V, and its recommended operating range caps output voltage at 36 V. Attempting to program above 36 V risks exceeding absolute maximum ratings and may cause permanent damage. The datasheet explicitly states "output voltage may be set at any level greater than 2.5 V up to 36 V" - this upper limit is enforced by internal breakdown margins and thermal constraints in the SOIC-8 package.
How does the LM431BCM's SOIC-8 package compare thermally to SOT-23 or TO-92 versions?
The LM431BCM in SOIC-8 (D package) has a junction-to-ambient thermal resistance (RθJA) of 126.9°C/W, significantly lower than the SOT-23 (267.7°C/W) and TO-92 (162.4°C/W) packages. This allows higher continuous power dissipation - up to 0.81 W at 25°C ambient - making the LM431BCM ideal for higher-current shunt applications where thermal headroom matters. Derating follows 6.5 mW/°C above 25°C ambient.
LM431BCM Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Texas Instruments
- Package/Case:
- 8-SOIC (0.154", 3.90mm Width)
- Series:
- -
- Packaging:
- Tube
- 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:
- ±1%
- 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
LM431BCM FAQ
1.How can I place an order for LM431BCM through Aetrix?
Please submit a Request for Quotation (RFQ) for LM431BCM 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 LM431BCM reliable?
The price and inventory of LM431BCM are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LM431BCM is usually 5 days.
3.What payment methods are accepted for LM431BCM?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LM431BCM transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LM431BCM?
LM431BCM orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LM431BCM 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 LM431BCM?
For technical support, including LM431BCM datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LM431BCM requirements.
6.How does Aetrix verify that LM431BCM is sourced from the original manufacturer or authorized distributors?
All LM431BCM 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 LM431BCM meets industry standards.
7.What is the process for return or replacement of LM431BCM?
All LM431BCM units undergo pre-shipment inspection (PSI). If there is an issue with LM431BCM, 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 LM431BCM part is unused and in its original packaging.
Return procedure for LM431BCM:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
LM431BCM Tags
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TL431AIDBZR
Texas Instruments
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TL431BQDBZR
Texas Instruments
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AN431AN-ATRG1
Diodes Incorporated
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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
Texas Instruments
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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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