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Texas Instruments LM431ACM/NOPB
- Part No.:
- LM431ACM/NOPB
- Manufacturer:
- Texas Instruments
- Category:
- Voltage Reference
- Package:
- 8-SOIC (0.154", 3.90mm Width)
- Datasheet:
-
LM431ACM/NOPB.pdf
- Description:
- IC VREF SHUNT ADJ 2.2% 8SOIC
- Quantity:
- Payment:
- Shipping:
Inventory:6,212
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Product details
Overview
LM431ACM/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 2.495 V reference voltage (±2.5 mV initial tolerance), supports 1–100 mA cathode current, operates from 2.5 V to 36 V output range, and maintains 50 ppm/°C average temperature coefficient over 0°C to 70°C. It is widely deployed in isolated flyback converters for secondary-side voltage regulation.
For engineers reviewing the LM431ACM/NOPB datasheet, LM431ACM/NOPB pinout, LM431ACM/NOPB application, or LM431ACM/NOPB equivalent, key selection criteria include its SOIC-8 package compatibility, guaranteed thermal stability across commercial temperature range, low dynamic impedance (0.75 Ω), fast turn-on response, and suitability for Zener replacement in precision voltage monitoring and current sink circuits.
Technical Context
The LM431ACM/NOPB functions as a 3-terminal adjustable shunt regulator with an internal bandgap reference and high-gain comparator driving an NPN output transistor. Its reference pin senses a fraction of cathode voltage via external resistor divider, enabling precise output programming from 2.5 V to 36 V. Regulation occurs by dynamically shunting cathode current to ground to maintain constant voltage at the reference node.
It operates in closed-loop mode with minimum 1 mA cathode current for stable regulation and supports open-loop comparator use. The device exhibits low-output noise, low dynamic output impedance (0.75 Ω typical), and temperature-compensated performance across its full operating range - critical for maintaining accuracy in feedback paths of isolated DC/DC converters.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Reference voltage (VREF) | 2.495 V ±2.5 mV at 10 mA - defines base accuracy of programmable output; enables 0.1% initial setting precision in voltage divider networks. |
| Output voltage range | 2.5 V to 36 V - set externally via two resistors; supports wide-range adaptability without changing IC in power supply designs. |
| Cathode current range | 1 mA to 100 mA - determines minimum load current needed for regulation and maximum shunt capability for error correction. |
| Average tempco | 50 ppm/°C - ensures ≤3.5 mV drift over 0°C–70°C; critical for stable feedback in temperature-varying environments. |
| Dynamic output impedance | 0.75 Ω - provides low AC impedance at cathode, minimizing output voltage ripple under transient load changes. |
| Reference input current | 2–4 μA - ultra-low bias current reduces divider network error and enables high-resistance feedback design for low power loss. |
| ESD rating (HBM) | ±2500 V - meets industrial handling requirements; allows safe assembly without special ESD precautions beyond standard practices. |
Pinout & Package
LM431ACM/NOPB is housed in an 8-pin SOIC (D) package measuring 4.90 mm × 3.91 mm, rated for commercial temperature range (0°C to 70°C), RoHS-compliant, with Sn lead finish and MSL Level-1 moisture sensitivity.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| Anode (Pins 2, 3, 6, 7) | Ground reference terminal | Internally tied together; must be connected to system ground to establish reference potential for regulation. |
| Cathode (Pin 1) | Shunt output / regulated voltage node | Connects to output rail; sinks variable current to maintain programmed voltage; carries full load + shunt current. |
| Reference (Pin 8) | Feedback sense input | High-impedance input (2–4 μA) that monitors divided output voltage; sets regulation point via external R1/R2 divider. |
| NC (Pins 4, 5) | No connect | Not internally bonded; must remain unconnected on PCB to avoid parasitic coupling or reliability risk. |
Key Features
| Feature | Design Value |
|---|---|
| Programmable output voltage | Set from 2.5 V to 36 V using only two external resistors - eliminates need for multiple fixed-voltage references in BOM. |
| Temperature-compensated reference | 50 ppm/°C average tempco over 0°C–70°C - ensures <±10 mV total drift in commercial applications without calibration. |
| Low dynamic output impedance | 0.75 Ω typical - improves transient response and reduces output ripple in feedback-controlled power stages. |
| Fast turn-on response | Enables rapid regulation recovery after line/load transients - essential for stable operation in digitally controlled or burst-mode supplies. |
| Space-saving SOIC-8 package | 4.90 mm × 3.91 mm footprint - offers higher power dissipation (0.81 W) than SOT-23 while maintaining compact layout for dense PCBs. |
Applications
| Isolated Flyback Power Supply | Voltage Monitoring Circuit |
|---|---|
|
Use Scenario: Secondary-side voltage regulation in AC/DC adapters and telecom power modules with optocoupler feedback. IC Role / Device Role / Timing Role: Precision shunt reference providing error signal to optocoupler LED driver; replaces discrete Zener + transistor. Use Value: Enables ±1% output accuracy over line, load, and temperature; SOIC-8 thermal margin supports continuous 100 mA shunt current at 70°C ambient. |
Use Scenario: Overvoltage detection in battery management systems or industrial PLC inputs. IC Role / Device Role / Timing Role: Adjustable threshold comparator with hysteresis; triggers protection circuit when input exceeds setpoint. Use Value: Programmable trip point (e.g., 12.6 V for 3S Li-ion) with 50 ppm/°C stability ensures reliable fault detection across operating temperature. |
| Current Sink / Source | Zener Diode Replacement |
|
Use Scenario: Constant-current LED driver or sensor bias circuit requiring stable 10–50 mA output. IC Role / Device Role / Timing Role: Shunt-regulated current source where cathode current equals (VREF/RSET); reference pin grounded. Use Value: Delivers <±2% current accuracy over temperature due to low tempco and minimal IREF drift - superior to standard Zeners. |
Use Scenario: Replacing 3.3 V or 5.1 V Zener diodes in legacy analog circuits needing improved stability. IC Role / Device Role / Timing Role: Drop-in functional replacement with identical 3-pin TO-92/SOT-23 footprints available; SOIC-8 variant offers better thermal performance. Use Value: Reduces voltage drift by >5× versus standard Zeners (50 ppm/°C vs. 200–500 ppm/°C), improving long-term measurement accuracy. |
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 2.495 V reference, but 0.5 Ω dynamic impedance and −1.4 mV/V ΔVREF/ΔVZ; SOIC-8, same pinout. | Higher accuracy (0.5% vs. 1%) and lower impedance improve regulation in high-precision feedback loops. | Select TL431ACDR when tighter output tolerance and lower AC impedance are required; pin-compatible upgrade path. |
| LM431AIM/NOPB | Identical electrical specs but rated for −40°C to 85°C industrial temperature range; same SOIC-8 package. | Supports extended ambient operation in automotive or outdoor equipment where commercial-grade parts may fail. | Choose LM431AIM/NOPB for designs requiring guaranteed performance beyond 70°C ambient - no layout change needed. |
Compared with LM431ACM/NOPB, TL431ACDR offers enhanced regulation fidelity for high-accuracy power supplies, while LM431AIM/NOPB extends operational reliability into harsher thermal environments - both retain full pin and functional compatibility.
Availability
LM431ACM/NOPB is available at Aetrix Electronics and suitable for isolated power supplies, voltage monitoring systems, and precision current sink circuits requiring stable component supply across production lifecycles.
Supply support for LM431ACM/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, embedded processing, and power management technologies, with decades of expertise in precision reference and power control ICs.
The LM431 product line was designed specifically for high-stability, adjustable shunt regulation in cost-sensitive power supply feedback paths - balancing accuracy, thermal performance, and ease of implementation across consumer, industrial, and telecom applications.
FAQ
What is the reference voltage tolerance of LM431ACM/NOPB at 25°C?
The LM431ACM/NOPB has a reference voltage (VREF) of 2.495 V with a tolerance of ±2.5 mV at 25°C and 10 mA cathode current, corresponding to ±0.1% initial accuracy. This value is specified for the 'A' grade variant and confirmed in the Electrical Characteristics table of the SNVS020H datasheet. The LM431ACM/NOPB achieves this tight tolerance through laser-trimmed internal resistors and bandgap compensation.
Can LM431ACM/NOPB be used in place of a standard Zener diode?
Yes, LM431ACM/NOPB serves as a direct functional replacement for Zener diodes in most applications. Unlike passive Zeners, it provides sharp turn-on, programmable voltage (2.5–36 V), low dynamic impedance (0.75 Ω), and 50 ppm/°C temperature stability - significantly improving regulation accuracy and thermal drift. The LM431ACM/NOPB requires only two external resistors to set output voltage and draws minimal reference current (2–4 μA).
What is the minimum cathode current required for regulation in LM431ACM/NOPB?
The LM431ACM/NOPB requires a minimum cathode current (IZ(MIN)) of 1 mA to maintain regulation, as specified under Recommended Operating Conditions. Below this threshold, the device exits regulation and output voltage becomes unstable. This 1 mA requirement is consistent across all LM431 variants and is critical for designing the series resistor (RS) in shunt regulator configurations to ensure worst-case operation remains within regulation bounds.
Does LM431ACM/NOPB support operation above 70°C ambient temperature?
No, LM431ACM/NOPB is rated for commercial temperature range only: 0°C to 70°C ambient. For operation beyond 70°C, TI recommends LM431AIM/NOPB (−40°C to 85°C) or LM431AIZ/NOPB (TO-92, −40°C to 85°C). Exceeding 70°C ambient with LM431ACM/NOPB risks parametric shift and potential thermal shutdown; its SOIC-8 package has RθJA = 126.9°C/W, limiting usable power dissipation at elevated temperatures.
How does the dynamic output impedance of LM431ACM/NOPB affect power supply stability?
The LM431ACM/NOPB's dynamic output impedance of 0.75 Ω (typical) directly impacts loop gain and phase margin in feedback-controlled power supplies. Lower impedance improves high-frequency rejection of ripple and noise on the cathode node, reducing output voltage perturbation during transients. In combination with its fast turn-on response and low reference current, this enables stable optocoupler-coupled feedback in isolated flyback converters without additional compensation components.
LM431ACM/NOPB Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Texas Instruments
- Package/Case:
- 8-SOIC (0.154", 3.90mm Width)
- Series:
- -
- Packaging:
- Tube
- 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:
- ±2.2%
- 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
LM431ACM/NOPB FAQ
1.How can I place an order for LM431ACM/NOPB through Aetrix?
Please submit a Request for Quotation (RFQ) for LM431ACM/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 LM431ACM/NOPB reliable?
The price and inventory of LM431ACM/NOPB are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LM431ACM/NOPB is usually 5 days.
3.What payment methods are accepted for LM431ACM/NOPB?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LM431ACM/NOPB transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LM431ACM/NOPB?
LM431ACM/NOPB orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LM431ACM/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 LM431ACM/NOPB?
For technical support, including LM431ACM/NOPB datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LM431ACM/NOPB requirements.
6.How does Aetrix verify that LM431ACM/NOPB is sourced from the original manufacturer or authorized distributors?
All LM431ACM/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 LM431ACM/NOPB meets industry standards.
7.What is the process for return or replacement of LM431ACM/NOPB?
All LM431ACM/NOPB units undergo pre-shipment inspection (PSI). If there is an issue with LM431ACM/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 LM431ACM/NOPB part is unused and in its original packaging.
Return procedure for LM431ACM/NOPB:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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