## General Description

The Fairchild Semiconductor LM431SACMLX is a programmable precision shunt voltage reference designed for high-accuracy voltage regulation and control applications. It operates as an adjustable three-terminal device capable of sinking current to maintain a stable reference voltage across external resistors. The LM431SACMLX features low temperature coefficient, low output voltage noise, and fast response to line and load changes. It is suitable for use in power supplies, voltage regulators, LED drivers, and instrumentation circuits requiring precision reference voltage with adjustable output. The device is supplied in a compact SOT-23-3 package, supporting space-constrained designs.

## Electrical Characteristics

* Reference Voltage (V_REF): 2.495 V typical at I_REF = 1 mA
* Adjustable Voltage Range: 2.495 V to 36 V
* Operating Cathode Current (I_K): 1 mA to 100 mA
* Output Impedance: 0.2 Ω typical at I_K = 10 mA
* Line Regulation: 0.01%/V typical
* Load Regulation: 0.2 mV typical for 1 mA change in I_K
* Temperature Coefficient: 50 ppm/°C typical
* Dynamic Output Impedance: 0.2 Ω at 10 kHz
* Input Bias Current: 0.2 μA typical
* Operating Voltage Range: 2.5 V to 36 V
* Noise Voltage: 50 μV RMS typical from 10 Hz to 10 kHz

## Package and Mechanical Features

* Package Type: SOT-23-3
* Lead Finish: Matte tin over copper alloy
* Mounting Style: Surface-mount, suitable for automated assembly
* Package Dimensions: 2.9 mm × 1.3 mm × 1.1 mm typical
* Thermal Resistance: 250°C/W junction-to-ambient typical in free air

## Performance Characteristics

* High-Precision Reference: Provides accurate and stable voltage with low temperature drift
* Adjustable Output Voltage: Configurable via external resistor network for flexible voltage regulation
* Low Output Impedance: Ensures minimal voltage drop and fast transient response for load changes
* Wide Operating Voltage and Current Range: Compatible with a broad variety of power supply voltages and currents
* Low Noise: Minimizes interference in sensitive analog circuits
* Fast Response Time: Capable of responding quickly to changes in input voltage or load current
* Reliable and Robust: Overvoltage and overcurrent tolerant within specification limits

## Applications

* Adjustable voltage regulators and shunt regulators
* Switching power supply voltage reference
* LED driver reference voltage control
* Battery-powered circuits requiring precise voltage reference
* Instrumentation and measurement systems
* Precision analog circuits and ADC/DAC reference voltage
* Power management ICs and feedback loop regulation

## Electrical Limits and Ratings

* Maximum Cathode Voltage: 36 V
* Minimum Cathode Voltage: 2.5 V
* Maximum Cathode Current: 100 mA
* Minimum Operating Current: 1 mA
* Maximum Junction Temperature: 125°C
* Operating Temperature Range: −40°C to +125°C
* Storage Temperature Range: −65°C to +150°C

## Key Advantages

* High-accuracy shunt voltage reference with low temperature coefficient suitable for precision applications
* Wide adjustable output voltage range allows flexible design for multiple systems
* Low dynamic output impedance provides fast response to load changes
* Low noise voltage supports sensitive analog signal applications
* Compact SOT-23-3 package enables space-efficient PCB designs
* Wide operating voltage and current range increases design versatility
* Reliable and stable operation over temperature and voltage variations enhances system robustness

The LM431SACMLX is a high-performance, programmable voltage reference ideal for precision regulation in power supplies, LED drivers, instrumentation, and other analog or mixed-signal applications where accurate, stable, and low-noise voltage is critical. Its combination of adjustable output, low temperature drift, and compact packaging makes it suitable for modern high-reliability embedded systems.