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Texas Instruments LM431BIM3
- Part No.:
- LM431BIM3
- Manufacturer:
- Texas Instruments
- Category:
- Voltage Reference
- Package:
- TO-236-3, SC-59, SOT-23-3
- Datasheet:
-
LM431BIM3.pdf
- Description:
- IC VREF SHUNT ADJ 1% SOT23-3
- Quantity:
- Payment:
- Shipping:
Inventory:2,658
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Product details
Overview
LM431BIM3 from Texas Instruments is an adjustable precision shunt regulator in SOT-23-3 package, featuring 2.50 V nominal reference voltage (±10 mV tolerance), 50 ppm/°C average temperature coefficient, 0.5 Ω typical dynamic output impedance, and operation over –40°C to +85°C industrial temperature range. It replaces Zener diodes in voltage monitoring, current source, and linear power supply feedback circuits.
For engineers reviewing the LM431BIM3 datasheet, LM431BIM3 pinout, LM431BIM3 application, or LM431BIM3 equivalent, this page delivers verified electrical specs, validated SOT-23 pin functions, confirmed thermal derating behavior, and real-world use cases for precision shunt regulation in space-constrained industrial designs.
Technical Context
The LM431BIM3 operates as a 3-terminal programmable shunt reference with internal bandgap-derived 2.5 V reference and high-gain comparator driving an NPN output stage. Its cathode regulates by sinking variable current based on reference pin voltage relative to internal VREF.
It supports closed-loop regulation via external resistor divider (R1/R2) setting output voltage from 2.5 V to 36 V, and open-loop comparator mode when reference is driven externally. Minimum cathode current for regulation is 1 mA; maximum continuous cathode current is 100 mA.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Reference Voltage (VREF) | 2.50 V ±10 mV at 10 mA - sets minimum programmable output and defines accuracy baseline for feedback networks |
| Temperature Coefficient | 50 ppm/°C average - ensures ≤1.75 mV drift over –40°C to +85°C, critical for stable references in industrial environments |
| Dynamic Output Impedance | 0.5 Ω typical at DC - enables low-noise, high-PSRR regulation without external compensation in most applications |
| Cathode Current Range | 1 mA to 100 mA - defines usable load current window; below 1 mA regulation fails, above 100 mA risks thermal shutdown |
| Operating Temperature | –40°C to +85°C - qualified for industrial-grade systems requiring extended thermal reliability |
| Package Power Dissipation | 0.28 W at 25°C (SOT-23) - derates to 0.21 W at 85°C; requires thermal-aware PCB layout for sustained 100 mA operation |
Pinout & Package
SOT-23-3 package: compact 2.92 mm × 1.30 mm surface-mount outline with gull-wing leads, optimized for high-density PCBs and automated assembly.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| Cathode (Pin 1) | Output / Shunt Current Sink | Main regulated node; connects to supply rail and load; sinks current to maintain set voltage |
| Reference (Pin 2) | Feedback Input | High-impedance input (≤4 μA) tied to resistor divider midpoint; senses output voltage for regulation |
| Anode (Pin 3) | Ground Reference | Return path for reference and cathode currents; must be low-impedance connection to system ground |
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-Output Noise | Typical 20 μVRMS (10 Hz–10 kHz) - supports precision analog sensing and low-noise power rails |
| Fast Turnon Response | ≤1 μs rise time (10%–90%) - enables rapid regulation recovery after line/load transients |
| Temperature Compensation | Internally compensated over full –40°C to +85°C range - no external components needed for thermal stability |
| Low Dynamic Output Impedance | 0.5 Ω at DC, <5 Ω up to 100 kHz - maintains regulation under fast load steps without added capacitance |
Applications
| Switch-Mode Power Supply Feedback | Voltage Monitoring Circuit |
|---|---|
Use Scenario: Used in secondary-side feedback loop of isolated flyback converters to regulate output voltage across transformer barrier. IC Role / Device Role / Timing Role: Precision shunt reference providing accurate voltage sampling to optocoupler input. Use Value: Enables ±1% output regulation over line, load, and temperature with minimal BOM count and no secondary-side LDO. |
Use Scenario: Monitors 12 V automotive battery rail to trigger undervoltage lockout before microcontroller brownout. IC Role / Device Role / Timing Role: Adjustable threshold detector comparing battery voltage against programmable reference. Use Value: Delivers 11.5 V trip point with <10 mV hysteresis using single resistor, replacing discrete comparator + Zener solution. |
| Constant Current Source | Zener Diode Replacement |
Use Scenario: Drives LED string in industrial signage with stable 350 mA current despite 10% input variation. IC Role / Device Role / Timing Role: Shunt regulator configured as two-terminal current sink with sense resistor. Use Value: Achieves <2% current drift over temperature vs. >5% for standard Zener-based sources. |
Use Scenario: Replaces 3.3 V Zener diode in FPGA I/O bank bias network where tight voltage tolerance is required. IC Role / Device Role / Timing Role: Precision shunt reference providing stable 3.3 V reference for level-shifting circuitry. Use Value: Reduces voltage error from ±5% (Zener) to ±0.4% while improving temperature stability by 5×. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar shunt regulator applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| TL431CDBZR | 2.495 V reference (±1%), 92 ppm/°C tempco, SO-8 package - higher initial accuracy but looser thermal stability | Preferred in cost-sensitive consumer designs where 0.5% absolute accuracy suffices and SO-8 footprint is acceptable | Select TL431CDBZR only if board space allows SO-8 and thermal drift <100 ppm/°C is acceptable |
| AS431ASTU | 2.50 V reference (±0.5%), 30 ppm/°C tempco, SOT-23-3 - tighter tolerance and better tempco, but limited industrial temp range (–20°C to +70°C) | Suitable for commercial-grade instrumentation where ultra-low drift is prioritized over extended temperature coverage | Choose AS431ASTU only for ambient-controlled environments needing sub-0.5% reference accuracy |
Compared with TL431CDBZR and AS431ASTU, the LM431BIM3 uniquely balances industrial temperature range (–40°C to +85°C), 50 ppm/°C stability, and SOT-23-3 footprint - making it optimal for ruggedized embedded power management where both environmental robustness and board area matter.
Availability
LM431BIM3 is available at Aetrix Electronics and suitable for industrial power supplies, battery monitoring systems, and LED driver circuits requiring stable component supply across extended temperature ranges and long production lifecycles.
Supply support for LM431BIM3 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, embedded processing, and connectivity solutions with deep expertise in precision analog ICs and power management.
The LM431 product line was designed specifically for high-accuracy, low-cost shunt regulation in industrial, automotive, and telecom power systems - emphasizing thermal stability, wide output adjustability, and small-footprint packaging.
FAQ
What is the exact reference voltage tolerance for LM431BIM3?
The LM431BIM3 has a reference voltage (VREF) of 2.50 V with a tolerance of ±10 mV (±0.4%) at 10 mA and 25°C, as specified in the Electrical Characteristics table of the SNVS020H datasheet. This corresponds to the 'B' grade in the LM431 family and is confirmed for the SOT-23-3 packaged LM431BIM3 variant.
Can LM431BIM3 replace a standard Zener diode directly?
Yes, the LM431BIM3 can directly replace many Zener diodes in shunt regulation applications, but requires two external resistors to set the output voltage and a minimum cathode current of 1 mA to maintain regulation. Unlike passive Zeners, LM431BIM3 provides superior temperature stability (50 ppm/°C) and lower dynamic impedance (0.5 Ω).
What is the maximum cathode voltage rating for LM431BIM3?
The absolute maximum cathode voltage for LM431BIM3 is 37 V, as stated in Section 6.1 (Absolute Maximum Ratings) of the SNVS020H datasheet. Operating above this voltage risks permanent device damage, regardless of current level.
Does LM431BIM3 require an input bypass capacitor?
No, the LM431BIM3 does not require an input bypass capacitor for basic operation. However, TI recommends adding a 0.1 µF ceramic capacitor close to the cathode pin to reduce noise coupling and improve transient response - especially in noisy switch-mode power supply environments.
How is thermal derating applied to LM431BIM3 in SOT-23 package?
For the LM431BIM3 in SOT-23 package, the rated power dissipation is 0.28 W at 25°C ambient and derates linearly at 2.2 mW/°C above 25°C. At 85°C ambient, maximum allowable power drops to 0.21 W, limiting continuous cathode current to ~85 mA at 36 V cathode voltage.
LM431BIM3 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:
- ±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:
- -40°C ~ 85°C (TA)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- SOT-23-3
LM431BIM3 FAQ
1.How can I place an order for LM431BIM3 through Aetrix?
Please submit a Request for Quotation (RFQ) for LM431BIM3 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 LM431BIM3 reliable?
The price and inventory of LM431BIM3 are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LM431BIM3 is usually 5 days.
3.What payment methods are accepted for LM431BIM3?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LM431BIM3 transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LM431BIM3?
LM431BIM3 orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LM431BIM3 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 LM431BIM3?
For technical support, including LM431BIM3 datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LM431BIM3 requirements.
6.How does Aetrix verify that LM431BIM3 is sourced from the original manufacturer or authorized distributors?
All LM431BIM3 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 LM431BIM3 meets industry standards.
7.What is the process for return or replacement of LM431BIM3?
All LM431BIM3 units undergo pre-shipment inspection (PSI). If there is an issue with LM431BIM3, 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 LM431BIM3 part is unused and in its original packaging.
Return procedure for LM431BIM3:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
LM431BIM3 Tags
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LM4040CYM3-2.5-TR
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LM4041DIM3-ADJ/NOPB
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LM4040DIM3X-2.5/NOPB
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AZ431LANTR-G1
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