LM431SACMFX

Voltage Reference Overview

The LM431SACMFX is a programmable shunt regulator manufactured by onsemi, formerly Fairchild Semiconductor. It functions as a three-terminal adjustable voltage reference with an internal reference voltage of approximately 2.5V. The output voltage is programmable from V_REF to 36V using two external resistors. Key electrical parameters include an initial accuracy of 2%, a temperature coefficient of 50 PPM/°C, and a maximum cathode current of 100 mA. The device operates within a temperature range of -25°C to +85°C and features a low dynamic output impedance of 0.2Ω typical. It is housed in an SOT-23F-3 surface-mount package.

Voltage Reference Feature Summary

• Programmable output voltage capability up to 36 volts via external resistor network
• Low dynamic output impedance for stable regulation performance
• Active output circuit provides sharp turn-on characteristics
• Thermal stability compensated over the full rated operating temperature range

Voltage Reference Applications

• Replacement for Zener diodes in voltage reference circuits
• Precision power supply feedback loops
• Portable equipment voltage monitoring

Voltage Reference Procurement Notes

Verify component authenticity through authorized distribution channels due to historical manufacturer transitions. Confirm RoHS compliance status as indicated in official datasheets. Check for End-of-Life (EOL) notifications or production discontinuation notices from onsemi. Ensure the SOT-23F-3 package footprint matches PCB design requirements. Validate that the specific suffix 'FX' corresponds to the correct tape-and-reel packaging configuration for automated assembly.

Voltage Reference Selection Notes

Select this component when a compact, adjustable shunt regulator is required for space-constrained designs. The SOT-23F-3 package offers a small form factor suitable for surface-mount technology. Consider the 2% initial accuracy and 50 PPM/°C temperature coefficient for applications requiring moderate precision. Ensure the operating current range between 1 mA and 100 mA aligns with the circuit's load requirements. Verify compatibility with the system's voltage headroom constraints up to 36V.

Voltage Reference Part Context

The LM431 series is a widely used family of programmable shunt regulators originally developed by Fairchild Semiconductor. Following onsemi's acquisition of Fairchild's semiconductor business, these parts are now produced and supported by onsemi. The LM431SA variant specifically denotes a version with 2% initial accuracy. This component serves as a direct functional equivalent to other industry-standard adjustable references like the TL431, maintaining pinout and electrical compatibility across manufacturers.

Voltage Reference Replacement Considerations

• LM431SAIMFX
• KA431