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Texas Instruments LM431BCM3X
- Part No.:
- LM431BCM3X
- Manufacturer:
- Texas Instruments
- Category:
- Voltage Reference
- Package:
- TO-236-3, SC-59, SOT-23-3
- Datasheet:
-
LM431BCM3X.pdf
- Description:
- IC VREF SHUNT ADJ 1% SOT23-3
- Quantity:
- Payment:
- Shipping:
Inventory:3,268
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Product details
Overview
LM431BCM3X from Texas Instruments is a precision adjustable shunt voltage regulator in SOT-23-3 package, featuring 2.5 V reference voltage (VREF), ±17 mV reference voltage deviation over temperature, 0.5 Ω dynamic output impedance, and 1 mA minimum cathode current for regulation - used in feedback loops of linear and switching power supplies requiring stable 2.5–36 V programmable output.
For engineers reviewing the LM431BCM3X datasheet, LM431BCM3X pinout, LM431BCM3X application, or LM431BCM3X equivalent, this page delivers verified electrical specs, thermal derating guidance, SOT-23 terminal mapping, and real-world implementation constraints for voltage monitoring, current sinking, and Zener replacement designs.
Technical Context
The LM431BCM3X operates as a 3-terminal adjustable shunt regulator with internal bandgap reference and error amplifier. Its reference pin senses external resistor-divider voltage; cathode shunts excess current to maintain regulated output. It functions in closed-loop mode (voltage regulation) or open-loop mode (comparator), with guaranteed operation from 1 mA to 100 mA cathode current.
Temperature compensation ensures stable 50 ppm/°C average TC across 0°C to 70°C. The device exhibits low-output noise and fast turnon response due to its bipolar process architecture and optimized internal gain stage - enabling use in precision references and feedback paths where Zener diodes lack stability or adjustability.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Reference Voltage (VREF) | 2.485–2.51 V at 10 mA - defines minimum programmable output (2.5 V) and sets accuracy baseline for resistor-divider design |
| Reference Voltage Deviation | ±17 mV over full 0°C to 70°C range - limits output drift in ambient-temperature-varying applications |
| Dynamic Output Impedance | 0.5 Ω at DC - ensures tight regulation under load transients without external compensation |
| Min Cathode Current (IZ(MIN)) | 0.4–1 mA - determines smallest series resistor value needed to sustain regulation at lowest input voltage |
| Max Cathode Current | 150 mA absolute max, 100 mA recommended operating - defines thermal limit and safe continuous shunt capacity |
| Temperature Coefficient | 50 ppm/°C average - enables <±0.35% total output variation across commercial temperature range |
| ESD Rating (HBM) | ±2500 V - requires standard ESD handling but no special protection circuitry in board layout |
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. Thermal resistance RθJA = 267.7°C/W; derate above 25°C at 2.2 mW/°C.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| Cathode (Pin 1) | Output / Shunt Current Sink | Main regulated node; connects to supply rail via series resistor and to load; carries full shunt current |
| Reference (Pin 2) | Feedback Input | High-impedance (≤4 μA) input sensing resistor-divider junction; sets output voltage via VOUT = VREF(1 + R1/R2) |
| Anode (Pin 3) | Ground Reference | Return path for reference current and shunt current; must be low-impedance connection to system ground |
Key Features
| Feature | Design Value |
|---|---|
| Adjustable Output Range | 2.5 V to 36 V - achieved with two external resistors; eliminates need for multiple fixed Zener values |
| Low Reference Input Current | 2–4 μA typical - minimizes divider current error and enables high-resistance feedback networks |
| Fast Turnon Response | Enables stable startup in switching PSUs and quick recovery after overvoltage events |
| Low-Output Noise | Supports precision analog circuits and ADC references where Zener noise would degrade SNR |
| Space-Saving SOT-23 | 2.92 mm × 1.30 mm footprint - ideal for compact power modules and dense PCB layouts |
Applications
| Adjustable Power Supply Feedback | Voltage Monitoring Circuit |
|---|---|
Use Scenario: Regulating output of isolated flyback or buck converter by feeding sampled output voltage into LM431BCM3X reference pin via resistor divider. IC Role / Device Role / Timing Role: Precision shunt regulator acting as error amplifier and voltage reference in optocoupler-coupled feedback loop. Use Value: Enables ±1% output accuracy over line/load/temperature with minimal external components and no secondary-side controller IC. | Use Scenario: Detecting overvoltage condition on a 12 V rail using LM431BCM3X configured as comparator with hysteresis. IC Role / Device Role / Timing Role: Adjustable threshold detector comparing rail voltage against internal 2.5 V reference. Use Value: Triggers crowbar or shutdown at precisely defined trip point (e.g., 13.2 V) without dedicated supervisor IC. |
| Current Sink / Source | Zener Diode Replacement |
Use Scenario: Providing constant 10 mA sink for LED bias or sensor excitation in industrial sensor interface. IC Role / Device Role / Timing Role: Programmable current regulator using cathode-anode path with single series resistor. Use Value: Delivers stable current independent of supply variation (15–30 V), with 50 ppm/°C tempco vs. >100 ppm/°C for discrete Zeners. | Use Scenario: Replacing 3.3 V Zener in microcontroller reset circuit where tighter tolerance and lower leakage are required. IC Role / Device Role / Timing Role: Precision shunt reference replacing passive Zener with superior tempco and dynamic impedance. Use Value: Reduces reset threshold drift from ±5% to ±0.7%, improving system reliability across temperature extremes. |
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 2.5 V reference, ±1% initial tolerance (vs. LM431BCM3X's ±1.2%), lower 0.2 Ω rZ, higher 100 mA IZ(MAX) | Preferred for high-accuracy feedback where tighter VREF tolerance is critical; identical SOT-23-3 pinout | Select TL431ACDBVR when ±1% output regulation is mandatory and thermal margin allows 0.2 W dissipation |
| AS431ASTZTR-G1 | 2.5 V reference, ±2% tolerance, 1.5 Ω rZ, 100 mA IZ(MAX), -40°C to 125°C rating | Better high-temp operation; suited for automotive under-hood monitoring where LM431BCM3X's 70°C max is insufficient | Choose AS431ASTZTR-G1 for extended temperature environments despite higher dynamic impedance |
Compared with TL431ACDBVR and AS431ASTZTR-G1, the LM431BCM3X offers optimal balance of cost, commercial-temperature performance, and proven stability in power supply feedback - making it ideal for cost-sensitive industrial and consumer designs where ±1.2% accuracy suffices.
Availability
LM431BCM3X is available at Aetrix Electronics and suitable for adjustable power supplies, voltage monitors, current sinks, and Zener replacements requiring stable component supply with RoHS-compliant green packaging and traceable sourcing.
Supply support for LM431BCM3X 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, with leadership in power management, signal chain, and precision analog technologies.
The LM431 product line was designed specifically for precision shunt regulation in space-constrained power systems - targeting cost-effective, thermally stable alternatives to discrete Zener diodes in commercial-grade power conversion and monitoring applications.
FAQ
What is the maximum cathode voltage rating for LM431BCM3X?
The LM431BCM3X has an absolute maximum cathode voltage rating of 37 V. Operation above this level risks permanent damage. For reliable long-term use, the recommended maximum cathode voltage is 36 V, aligned with its specified output programming range and thermal limits in the SOT-23 package.
Does LM431BCM3X require an external capacitor for stability?
No, the LM431BCM3X does not require an external capacitor for basic shunt regulation. However, TI recommends a 0.1 µF ceramic bypass capacitor near the cathode if input noise exceeds 10 mVpp, as unfiltered ripple can modulate the reference node and degrade output accuracy. Stability boundaries depend on external resistor values and load capacitance - see Figure 2 in SNVS020H.
How is the output voltage calculated for LM431BCM3X in a typical application?
The output voltage for LM431BCM3X is calculated using VO = VREF × (1 + R1/R2), where VREF is 2.485–2.51 V at 25°C. For example, with R1 = 2.49 kΩ and R2 = 1 kΩ, VO ≈ 2.5 V × 3.49 = 8.73 V. Note that VREF shifts slightly with cathode voltage (ΔVREF/ΔVZ ≈ −1.4 mV/V), so final accuracy requires correction per Equation 3 in SNVS020H.
Can LM431BCM3X replace a standard 5.1 V Zener diode directly?
Yes, LM431BCM3X can replace a 5.1 V Zener in most cases - but requires two external resistors (R1 = 1.02 kΩ, R2 = 1 kΩ) to set 5.1 V output, unlike the direct-drop-in nature of a Zener. It offers superior temperature stability (50 ppm/°C vs. >100 ppm/°C), lower dynamic impedance (0.5 Ω vs. 10–20 Ω), and programmability, though layout must accommodate the 3-pin SOT-23 footprint.
What is the thermal derating slope for LM431BCM3X in SOT-23 package?
The LM431BCM3X in SOT-23 package has a thermal derating slope of 2.2 mW/°C above 25°C ambient. With a maximum internal power dissipation of 0.28 W at 25°C, usable power drops to 0.258 W at 35°C and 0.214 W at 60°C. This must be factored into series resistor selection to avoid exceeding 150°C junction temperature.
LM431BCM3X 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:
- 0°C ~ 70°C (TA)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- SOT-23-3
LM431BCM3X FAQ
1.How can I place an order for LM431BCM3X through Aetrix?
Please submit a Request for Quotation (RFQ) for LM431BCM3X 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 LM431BCM3X reliable?
The price and inventory of LM431BCM3X are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LM431BCM3X is usually 5 days.
3.What payment methods are accepted for LM431BCM3X?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LM431BCM3X transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LM431BCM3X?
LM431BCM3X orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LM431BCM3X 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 LM431BCM3X?
For technical support, including LM431BCM3X datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LM431BCM3X requirements.
6.How does Aetrix verify that LM431BCM3X is sourced from the original manufacturer or authorized distributors?
All LM431BCM3X 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 LM431BCM3X meets industry standards.
7.What is the process for return or replacement of LM431BCM3X?
All LM431BCM3X units undergo pre-shipment inspection (PSI). If there is an issue with LM431BCM3X, 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 LM431BCM3X part is unused and in its original packaging.
Return procedure for LM431BCM3X:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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