LM431SACM3X

Voltage Reference Overview

The LM431SACM3X is a three-terminal programmable shunt regulator manufactured by onsemi. It operates within a cathode voltage range of VREF to 36 V and supports a continuous cathode current from 1 mA to 100 mA. The device features a reference input voltage (VREF) typically at 2.5 V with an initial accuracy of 2%. It exhibits a typical dynamic output impedance of 0.2 Ω and a full-range temperature coefficient of 50 ppm/°C. The component functions over an operating temperature range of -25°C to +85°C and is housed in a SOT-23 surface-mount package.

Voltage Reference Feature Summary

• Programmable output voltage adjustable between the internal reference voltage and 36 V using two external resistors
• Temperature compensated for stable operation across the full rated operating temperature range
• Active output circuit provides sharp turn-on characteristics suitable for replacing Zener diodes
• Low dynamic output impedance and low output noise voltage

Voltage Reference Applications

• Shunt regulator circuits
• Output control for three-terminal fixed regulators
• High current shunt regulator configurations
• Current limit or current source applications
• Constant-current sink designs

Voltage Reference Procurement Notes

Verify the specific suffix 'M3' corresponds to the SOT-23 package variant, as ordering information lists multiple package options including SOT-23FL and SOT-89. Confirm that the 'SA' designation aligns with the required 2% initial accuracy and -25°C to +85°C operating temperature range rather than the industrial grade variants. Ensure compatibility with RoHS compliance requirements prior to procurement.

Voltage Reference Selection Notes

Select this component when a precise, adjustable voltage reference is required in a compact surface-mount form factor. The LM431SACM3X is appropriate for designs needing a sharp turn-on response and low dynamic impedance. Consider the 2% initial accuracy and 50 ppm/°C temperature coefficient against application tolerance requirements. Verify that the maximum cathode voltage of 36 V and current capability of 100 mA meet the circuit load demands.

Voltage Reference Part Context

The LM431 series comprises three-terminal adjustable regulators designed for thermal stability. The LM431SA, LM431SB, and LM431SC variants differ primarily in output voltage tolerance. The LM431SACM3X specifically belongs to the SA family, offering 2% accuracy. This part serves as a direct replacement for standard Zener diodes in many precision regulation applications due to its active output stage and programmability.

Voltage Reference Replacement Considerations

The datasheet notes that certain devices have been discontinued. Verify availability status for the LM431SACM3X specifically. Cross-reference pinouts for SOT-23 packages across manufacturers to ensure Cathode, Reference, and Anode alignment matches the target design schematic.