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Texas Instruments LM431BCMX/NOPB
- Part No.:
- LM431BCMX/NOPB
- Manufacturer:
- Texas Instruments
- Category:
- Voltage Reference
- Package:
- 8-SOIC (0.154", 3.90mm Width)
- Datasheet:
-
LM431BCMX/NOPB.pdf
- Description:
- IC VREF SHUNT ADJ 1% 8SOIC
- Quantity:
- Payment:
- Shipping:
Inventory:7,155
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Product details
Overview
LM431BCMX/NOPB from Texas Instruments is a precision adjustable shunt regulator IC used as a programmable voltage reference or error amplifier in feedback loops of linear and switching power supplies. It delivers 2.5 V reference voltage (±10 mV tolerance), supports 1–100 mA cathode current, operates up to 36 V cathode voltage, and maintains 50 ppm/°C average temperature coefficient across 0°C to 70°C. It replaces Zener diodes in voltage monitoring and current sink circuits.
For engineers reviewing the LM431BCMX/NOPB datasheet, LM431BCMX/NOPB pinout, LM431BCMX/NOPB application, or LM431BCMX/NOPB equivalent, this page provides verified package mapping (SOIC-8), confirmed electrical specs including dynamic impedance (0.5 Ω), thermal resistance (126.9 °C/W), and real-world design context for shunt regulation, overvoltage protection, and precision current sourcing.
Technical Context
The LM431BCMX/NOPB implements a bandgap-based reference core with internal error amplifier and NPN output stage, enabling precise shunt regulation via external resistor divider on the REF pin. Its operation requires only 1 mA minimum cathode current to maintain regulation and exhibits fast turn-on response due to low-output noise and sharp knee characteristics.
It functions in closed-loop mode where REF senses output voltage through R1/R2, adjusting cathode current to hold VOUT = VREF × (1 + R1/R2); open-loop comparator use is also supported. The SOIC-8 package includes NC pins (4,5) and supports stable operation with optional input/output bypass capacitors.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Reference voltage (VREF) | 2.50 V ±10 mV at 10 mA - sets base accuracy for programmable output voltage calculation |
| Cathode voltage range | 2.5 V to 36 V - enables wide-range adjustable regulation without external series pass transistor |
| Min/max cathode current | 1 mA to 100 mA - defines stable regulation envelope; below 1 mA, device exits regulation |
| Dynamic output impedance | 0.5 Ω at DC - ensures tight load regulation and low output voltage drift under varying current |
| Avg. temp. coefficient | 50 ppm/°C - guarantees ≤1.75 mV drift over 0°C–70°C ambient, critical for precision references |
| Reference input current | 2–4 μA - enables high-impedance feedback networks with minimal loading error |
| ESD rating (HBM) | ±2500 V - meets industrial handling requirements without special ESD precautions beyond standard practice |
Pinout & Package
LM431BCMX/NOPB is housed in an 8-pin SOIC (D) package (4.90 mm × 3.91 mm body), rated for 0°C to 70°C operation and RoHS-compliant with Sn lead finish. Thermal resistance is 126.9 °C/W (junction-to-ambient), supporting up to 0.81 W internal power dissipation at 25°C ambient.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| Cathode (Pin 1) | Output node / shunt current path | Connects to regulated output rail; sinks variable current to maintain set voltage |
| Reference (Pin 2) | Feedback input | Senses divided output voltage; internal comparator compares to 2.5 V reference |
| Anode (Pins 3,6,7) | Ground return | Internally tied together; must be connected to system ground for proper biasing |
| NC (Pins 4,5) | No internal connection | Not bonded; left unconnected-no routing or grounding required |
Key Features
| Feature | Design Value |
|---|---|
| Programmable output voltage | Set from 2.5 V to 36 V using two external resistors-eliminates need for multiple fixed Zeners |
| Low dynamic output impedance | 0.5 Ω ensures <1 mV output shift per 2 mA load change-critical for stable feedback in SMPS |
| Temperature-compensated reference | 50 ppm/°C drift over full operating range-enables reliable performance in industrial environments |
| Fast turn-on response | Sharp knee characteristic allows rapid transition into regulation-reduces startup overshoot in power supplies |
| Low-output noise | Enables clean reference for ADCs, DACs, and analog comparators without added filtering |
Applications
| Adjustable Power Supply Regulation | Voltage Monitoring & Protection |
|---|---|
|
Use Scenario: Regulating 5 V output in isolated flyback converter with optocoupler feedback loop. IC Role / Device Role / Timing Role: Shunt regulator acting as secondary-side error amplifier; REF pin receives optocoupler-emitter voltage, Cathode drives optocoupler LED. Use Value: Enables precise 5 V ±1% regulation across line/load/temperature with no secondary LDO required. |
Use Scenario: Detecting overvoltage condition (>12.6 V) on automotive battery rail to trigger crowbar circuit. IC Role / Device Role / Timing Role: Precision voltage threshold detector; REF pin biased by resistor divider, Cathode triggers SCR gate when threshold exceeded. Use Value: Provides 12.6 V trip point with <±0.1 V tolerance and <10 μs response-prevents downstream damage. |
| Current Sink / Source Circuit | Zener Diode Replacement |
|
Use Scenario: Constant-current LED driver for industrial status indicators requiring 20 mA ±2% over 5–24 V input. IC Role / Device Role / Timing Role: Adjustable current sink; REF grounded, Cathode connected to LED anode, Anode to load return. Use Value: Delivers stable 20 mA independent of input voltage variation-replaces discrete transistor+Zener solution. |
Use Scenario: Replacing 3.3 V Zener in microcontroller reset circuit where temperature stability and low leakage are critical. IC Role / Device Role / Timing Role: Precision shunt reference; configured as 3.3 V via R1/R2, replacing 5% tolerance Zener diode. Use Value: Reduces reset threshold drift from ±150 mV (Zener) to ±33 mV (LM431BCMX/NOPB) over temperature. |
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 | 2.495 V reference (±0.5%), lower 0.2 Ω dynamic impedance, SOT-23-3 package | Better accuracy and smaller footprint; limited to 36 V max cathode voltage and 100 mA max current | Select TL431ACDR for space-constrained designs needing tighter reference tolerance and lower impedance |
| LM431AIMX/NOPB | Same 2.5 V reference but −40°C to 85°C extended temperature range; SOIC-8 package | Identical pinout and function; suitable for automotive or outdoor industrial deployments | Choose LM431AIMX/NOPB when operation below 0°C or above 70°C is required-no layout change needed |
Compared with TL431ACDR, LM431BCMX/NOPB trades 0.5% reference accuracy for broader commercial temperature support and SOIC-8 manufacturability; versus LM431AIMX/NOPB, it offers identical functionality at lower cost for 0°C–70°C applications.
Availability
LM431BCMX/NOPB is available at Aetrix Electronics and suitable for adjustable power supplies, voltage monitoring systems, and current sink circuits requiring stable component supply, consistent parametric performance, and long-term production continuity.
Supply support for LM431BCMX/NOPB 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 specializing in analog and embedded processing technologies, with decades of experience in precision reference and power management ICs.
The LM431 product line was designed for high-accuracy shunt regulation in cost-sensitive industrial and consumer power systems, offering Zener replacement capability with superior temperature stability and programmability.
FAQ
What is the reference voltage tolerance of LM431BCMX/NOPB?
The LM431BCMX/NOPB has a reference voltage (VREF) of 2.50 V with a tolerance of ±10 mV (±0.4%) at 10 mA cathode current and 25°C. This corresponds to the 'B' grade in the LM431 family, confirmed in Section 6.5 of the SNVS020H datasheet. The LM431BCMX/NOPB maintains this specification across its 0°C to 70°C operating range.
Can LM431BCMX/NOPB replace a standard Zener diode directly?
Yes, LM431BCMX/NOPB can directly replace many Zener diodes in shunt regulation applications, provided external resistors set the desired output voltage and minimum cathode current (≥1 mA) is maintained. Unlike passive Zeners, LM431BCMX/NOPB offers programmability, lower dynamic impedance (0.5 Ω vs typical 10–100 Ω), and tighter temperature stability (50 ppm/°C).
What is the maximum power dissipation for LM431BCMX/NOPB in SOIC-8 package?
The LM431BCMX/NOPB SOIC-8 package supports 0.81 W maximum internal power dissipation at 25°C ambient, derating linearly at 6.5 mW/°C above that temperature. This limit is defined by its junction-to-ambient thermal resistance of 126.9 °C/W and maximum junction temperature of 150°C, per Section 6.1 of the datasheet.
Does LM431BCMX/NOPB require external capacitors for stability?
No, LM431BCMX/NOPB does not require external capacitors for basic shunt regulation. However, TI recommends a 0.1 µF ceramic capacitor near the cathode for noise reduction in noisy environments. Stability boundaries depend on output capacitance and feedback network layout-see Figure 2 in the datasheet for oscillation risk zones.
How is the output voltage calculated for LM431BCMX/NOPB?
The output voltage (VOUT) of LM431BCMX/NOPB is calculated as VREF × (1 + R1/R2), where R1 connects cathode to reference pin and R2 connects reference pin to ground. For example, with R1 = R2 = 1 kΩ, VOUT = 2.5 V × 2 = 5.0 V. The LM431BCMX/NOPB's internal VREF shifts slightly with cathode voltage-correction terms are provided in Equation 3 of the datasheet.
LM431BCMX/NOPB Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Texas Instruments
- Package/Case:
- 8-SOIC (0.154", 3.90mm Width)
- Series:
- -
- Packaging:
- Tape & Reel (TR)
- Product Status:
- Active
- 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
LM431BCMX/NOPB FAQ
1.How can I place an order for LM431BCMX/NOPB through Aetrix?
Please submit a Request for Quotation (RFQ) for LM431BCMX/NOPB 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 LM431BCMX/NOPB reliable?
The price and inventory of LM431BCMX/NOPB are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LM431BCMX/NOPB is usually 5 days.
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LM431BCMX/NOPB orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LM431BCMX/NOPB 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 LM431BCMX/NOPB?
For technical support, including LM431BCMX/NOPB datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LM431BCMX/NOPB requirements.
6.How does Aetrix verify that LM431BCMX/NOPB is sourced from the original manufacturer or authorized distributors?
All LM431BCMX/NOPB 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 LM431BCMX/NOPB meets industry standards.
7.What is the process for return or replacement of LM431BCMX/NOPB?
All LM431BCMX/NOPB units undergo pre-shipment inspection (PSI). If there is an issue with LM431BCMX/NOPB, 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 LM431BCMX/NOPB part is unused and in its original packaging.
Return procedure for LM431BCMX/NOPB:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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