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Texas Instruments LM431BIM
- Part No.:
- LM431BIM
- Manufacturer:
- Texas Instruments
- Category:
- Voltage Reference
- Package:
- 8-SOIC (0.154", 3.90mm Width)
- Datasheet:
-
LM431BIM.pdf
- Description:
- IC VREF SHUNT ADJ 1% 8SOIC
- Quantity:
- Payment:
- Shipping:
Inventory:1,139
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Product details
Overview
LM431BIM from Texas Instruments is an adjustable precision shunt regulator IC with 2.5 V reference voltage, ±10 mV initial tolerance (B-grade), and guaranteed operation from –40°C to +85°C in SOIC-8 package. It delivers low dynamic output impedance (0.5 Ω), fast turn-on response, and temperature-stable regulation for linear/switching power supply feedback loops and voltage monitoring circuits.
For engineers reviewing the LM431BIM datasheet, LM431BIM pinout, LM431BIM application, or LM431BIM equivalent, this page provides verified electrical parameters, SOIC-8 terminal mapping, thermal derating guidance, stability boundary data, and validated alternative parts for industrial-grade shunt reference designs.
Technical Context
The LM431BIM operates as a 3-terminal programmable Zener replacement, using internal bandgap reference and transconductance amplifier to regulate cathode-to-anode voltage via external resistor divider on the REF pin. Its closed-loop mode requires ≥1 mA cathode current for stable regulation across 2.5–36 V output range.
It features average temperature coefficient of 50 ppm/°C, low-output noise, and thermal hysteresis induced by package stress-not device drift-making it suitable for precision feedback where long-term voltage repeatability matters more than ultra-low drift.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Reference voltage (VREF) | 2.50 V (typ), ±10 mV initial tolerance at 25°C - sets minimum programmable output voltage |
| Cathode voltage range | 2.5 V to 36 V - defines usable output span when configured with R1/R2 divider |
| Min/max cathode current | 1 mA to 100 mA - determines external series resistor sizing and load capability |
| Dynamic output impedance | 0.5 Ω (typ) - ensures tight regulation under varying load conditions |
| Temp coefficient | 50 ppm/°C (avg) - enables stable performance across –40°C to +85°C industrial range |
| Reference input current | 2–4 μA (typ) - minimizes divider current error and power loss |
| ESD rating (HBM) | ±2500 V - confirms robustness for standard handling without special ESD controls |
Pinout & Package
LM431BIM is housed in an 8-pin SOIC (D package) with 4.90 mm × 3.91 mm body size and gull-wing leads. Pins 4 and 5 are internally unconnected (NC); pins 2 and 8 serve as reference and cathode respectively, while pins 3, 6, and 7 are tied to anode internally.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| Pin 1 | Cathode | Main output node; sinks regulated current to maintain programmed voltage at cathode |
| Pins 2, 3, 6, 7 | Anode | Common ground return path; all internally shorted - must be connected to system GND |
| Pins 4, 5 | NC | No internal connection - leave floating or tie to GND per layout best practice |
| Pin 8 | Reference | Sense input for feedback divider; high-impedance node requiring clean routing away from noise sources |
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 diodes |
| Temperature-compensated reference | Stable over full –40°C to +85°C range with 50 ppm/°C avg TC - avoids external compensation circuitry |
| Low dynamic output impedance | 0.5 Ω typical - maintains regulation accuracy during transient load changes in power supplies |
| Fast turn-on response | Enables use in crowbar and overvoltage protection circuits requiring rapid clamping action |
| Space-saving SOIC-8 package | 4.90 mm × 3.91 mm footprint - supports high-density PCB layouts without sacrificing thermal performance (RθJA = 126.9°C/W) |
Applications
| Switch-Mode Power Supply Feedback | Voltage Monitoring & Protection |
|---|---|
Use Scenario: Secondary-side feedback loop in isolated flyback or forward converters operating from 5 V to 24 V outputs. IC Role / Device Role / Timing Role: Shunt regulator providing precise voltage reference to optocoupler input, enabling accurate output regulation across line/load variations. Use Value: Replaces discrete Zener + transistor combinations with single IC achieving ±1% output accuracy and reduced BOM count. | Use Scenario: Overvoltage detection circuit triggering shutdown in battery management systems or DC bus monitors. IC Role / Device Role / Timing Role: Precision threshold detector comparing sensed voltage against programmable trip point set by R1/R2 network. Use Value: Enables reliable 15 V overvoltage cutoff with <10 mV hysteresis and immunity to ambient temperature shifts. |
| Current Source/Sink Circuits | Zener Diode Replacement |
Use Scenario: Constant-current LED driver for industrial signage requiring stable 20 mA output over 12 V input range. IC Role / Device Role / Timing Role: Adjustable shunt regulator configured as two-terminal current source with cathode as output node. Use Value: Delivers 0.5% current stability across temperature versus discrete solutions suffering >3% drift. | Use Scenario: Voltage reference in analog sensor signal conditioning stages replacing 2.5 V Zener diodes. IC Role / Device Role / Timing Role: Precision shunt reference providing low-noise, low-impedance bias point for op-amp circuits. Use Value: Reduces output noise by 40% and improves PSRR by 15 dB compared to standard Zener diodes. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar shunt regulator applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| TL431CDBVR | Same 2.5 V reference but C-grade (±2% initial tolerance); SOT-23-3 package; lower max cathode current (100 mA vs 150 mA absolute max) | Better suited for cost-sensitive consumer applications with relaxed accuracy requirements; not rated for –40°C to +85°C industrial range | Select TL431CDBVR only if commercial temp range suffices and SOIC-8 footprint is unnecessary |
| AS431ASTU | Pin-compatible SOIC-8; ±1% initial tolerance (tighter than LM431BIM's ±0.4%); higher ESD rating (±4000 V HBM); same 2.5 V reference | Preferred for automotive or harsh-environment designs requiring enhanced reliability and tighter initial accuracy | Choose AS431ASTU when design mandates <±10 mV reference error or >±3000 V ESD immunity |
Compared with TL431CDBVR and AS431ASTU, the LM431BIM offers optimal balance of industrial temperature range, SOIC-8 thermal performance, and B-grade precision - making it ideal for legacy industrial power supplies where board space and thermal margin are constrained but extreme accuracy is not required.
Availability
LM431BIM is available at Aetrix Electronics and suitable for industrial power supplies, battery protection circuits, and precision analog references requiring stable component supply with full lifecycle support.
Supply support for LM431BIM 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 delivering analog and embedded processing solutions for industrial, automotive, and personal electronics markets.
The LM431 product line was designed specifically for precision shunt regulation in feedback loops and voltage monitoring applications - emphasizing temperature stability, low dynamic impedance, and compatibility with standard Zener-based designs.
FAQ
What is the maximum cathode voltage rating for LM431BIM?
The LM431BIM has an absolute maximum cathode voltage rating of 37 V. Operation above this level risks permanent damage. For reliable long-term use, TI specifies a recommended maximum cathode voltage of 36 V under normal operating conditions - aligning with its programmable output range and ensuring margin against transients.
Does LM431BIM require an external capacitor for stability?
No, LM431BIM does not require an external capacitor for basic regulation. However, TI recommends adding a 0.1-µF ceramic bypass capacitor near the cathode pin to reduce input noise that could affect output accuracy. Stability boundary curves in the datasheet show oscillation risk under certain R-C load conditions, so capacitor selection should follow Figure 2 guidelines when driving capacitive loads.
How is the output voltage calculated for LM431BIM in a shunt configuration?
The output voltage VO of LM431BIM is calculated as VO = VREF × (1 + R1/R2), where VREF is the internal reference voltage (2.50 V typ), and R1/R2 form the external feedback divider. For example, with R1 = 1 kΩ and R2 = 1 kΩ, VO = 5.0 V. Note that VREF varies slightly with cathode voltage (ΔVREF/ΔVZ ≈ −1.4 mV/V), so high-accuracy designs should apply correction per Equation 3 in the datasheet.
What is the minimum cathode current needed for regulation in LM431BIM?
The LM431BIM requires a minimum cathode current (IZ(MIN)) of 1 mA to maintain regulation. Below this threshold, the device exits regulation and output voltage drops. This value is specified across the full –40°C to +85°C temperature range and must be ensured under worst-case conditions - e.g., lowest input voltage and highest load current - when selecting the series resistor RS.
Can LM431BIM be used as a comparator?
Yes, LM431BIM can operate in open-loop mode as a comparator. When the reference pin is driven by an external voltage source instead of a resistor divider, the cathode switches between high-impedance and sinking states based on whether the applied voltage exceeds VREF. This enables applications like overvoltage detection and delay timers, though propagation delay and hysteresis must be verified per application circuit requirements.
LM431BIM 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:
- -40°C ~ 85°C (TA)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 8-SOIC
LM431BIM FAQ
1.How can I place an order for LM431BIM through Aetrix?
Please submit a Request for Quotation (RFQ) for LM431BIM 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 LM431BIM reliable?
The price and inventory of LM431BIM are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LM431BIM is usually 5 days.
3.What payment methods are accepted for LM431BIM?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LM431BIM transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LM431BIM?
LM431BIM orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LM431BIM 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 LM431BIM?
For technical support, including LM431BIM datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LM431BIM requirements.
6.How does Aetrix verify that LM431BIM is sourced from the original manufacturer or authorized distributors?
All LM431BIM 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 LM431BIM meets industry standards.
7.What is the process for return or replacement of LM431BIM?
All LM431BIM units undergo pre-shipment inspection (PSI). If there is an issue with LM431BIM, 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 LM431BIM part is unused and in its original packaging.
Return procedure for LM431BIM:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
LM431BIM Tags
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TL431AIDBZR
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TL431BQDBZR
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AN431AN-ATRG1
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LM4040CYM3-2.5-TR
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LM4040CYM3-4.1-TR
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LM4040EIM3-2.5/NOPB
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AZ431LBNTR-G1
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LM4040D20IDBZR
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LM4041DIM3-ADJ/NOPB
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LM4040DIM3X-2.5/NOPB
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LM4040DIM3-2.5/NOPB
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AZ431LANTR-G1
Diodes Incorporated
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