LM431SACMFX_G Equivalent & Substitute Parts

Part Overview

The LM431SACMFX_G is a shunt voltage reference IC with adjustable output from 2.5V to 36V, featuring ±2% tolerance and 100 mA output capability in a SOT-23F-3 surface mount package. This part is classified as obsolete, making equivalent and substitute parts necessary for new designs and ongoing production requirements. Substitute parts must maintain functional compatibility through matching electrical specifications and mechanical packaging standards.

Key Parameters

Parameter	Value
Reference Type	Shunt
Output Type	Adjustable
Voltage - Output (Min/Fixed)	2.5V
Voltage - Output (Max)	36V
Current - Output	100 mA
Tolerance	±2%
Temperature Coefficient	50 ppm/°C Typical
Current - Cathode	1 mA
Operating Temperature	-25°C to 85°C (TA)
Package / Case	SOT-23-3 Flat Leads
Mounting Type	Surface Mount

Substitute Part Grouping Explanation

Substitute parts for the LM431SACMFX_G are classified based on electrical parameter compatibility and packaging equivalence. The primary substitution criteria are:

Electrical Parameters (Critical for Substitution):

Reference type: Shunt
Output type: Adjustable
Voltage output range: 2.5V to 36V
Package / Case: SOT-23-3 Flat Leads or equivalent

Substitution Categories:

Category 1: Parametric Equivalents (Identical Electrical Specifications) Parts matching all critical electrical parameters including 100 mA output current, ±2% tolerance, and SOT-23F-3 packaging. These parts are direct functional replacements with no design modifications required.

Category 2: Functional Alternatives (Modified Electrical Specifications) Parts with the same reference type, output range, and package but differing in output current or tolerance specifications. These require circuit evaluation to confirm suitability for the application.

Parameter Comparison

Parameter	LM431SACMFX_G (Main)	LM431SACMFX	KA431SMF2TF	NCP431AISNT1G
Manufacturer	onsemi	Fairchild Semiconductor	Fairchild Semiconductor	onsemi
Product Status	Obsolete	Active	Active	Active
Reference Type	Shunt	Shunt	Shunt	Shunt
Output Type	Adjustable	Adjustable	Adjustable	Adjustable
Voltage - Output (Min/Fixed)	2.5V	2.5V	2.5V	2.5V
Voltage - Output (Max)	36V	36V	36V	36V
Current - Output	100 mA	100 mA	100 mA	40 µA
Tolerance	±2%	±2%	±2%	±1%
Temperature Coefficient	50 ppm/°C Typical	50 ppm/°C Typical	50 ppm/°C Typical	50 ppm/°C Typical
Current - Cathode	1 mA	1 mA	1 mA	100 mA
Operating Temperature	-25°C to 85°C	-25°C to 85°C	-25°C to 85°C	-40°C to 85°C
Package / Case	SOT-23-3 Flat Leads	SOT-23-3 Flat Leads	SOT-23-3 Flat Leads	SOT-23-3 (TO-236)
Mounting Type	Surface Mount	Surface Mount	Surface Mount	Surface Mount

Engineering Selection Recommendations

LM431SACMFX (Fairchild Semiconductor): Direct parametric equivalent with active product status. Identical electrical specifications and SOT-23-3 Flat Leads packaging. Recommended as primary substitute for obsolete LM431SACMFX_G.

KA431SMF2TF (Fairchild Semiconductor): Direct parametric equivalent with active product status. Matches all critical electrical parameters and packaging. Suitable for direct replacement in existing designs.

NCP431AISNT1G (onsemi): Functional alternative with active product status and improved tolerance (±1% vs ±2%). Output current specification differs (40 µA vs 100 mA), requiring circuit evaluation. Extended operating temperature range (-40°C to 85°C) provides broader environmental coverage. RoHS3 compliant and MSL Level 1 rating. Suitable where lower output current and tighter tolerance are acceptable.

Frequently Asked Questions (FAQ)

Q: Can NCP431AISNT1G replace LM431SACMFX_G directly? A: NCP431AISNT1G is functionally compatible for shunt voltage reference applications with the same output voltage range and package. However, the output current specification differs (40 µA vs 100 mA). Circuit evaluation is required to confirm suitability for your specific application requirements.

Q: What is the difference between SOT-23F-3 and SOT-23-3 (TO-236) packaging? A: Both are three-pin surface mount packages with identical pinout and footprint compatibility. SOT-23F-3 specifies flat leads, while SOT-23-3 (TO-236) is the standard designation. These are mechanically and electrically interchangeable.

Q: Why is LM431SACMFX_G obsolete? A: Product obsolescence is determined by manufacturer lifecycle decisions. Active substitutes with identical or superior specifications are available from multiple manufacturers.

Q: Which substitute offers the best compliance for new designs? A: LM431SACMFX and KA431SMF2TF both provide active product status with identical specifications. NCP431AISNT1G offers additional RoHS3 compliance and MSL Level 1 rating for moisture-sensitive applications.

Q: Are there tolerance differences between substitutes? A: LM431SACMFX and KA431SMF2TF maintain ±2% tolerance matching the original part. NCP431AISNT1G provides tighter ±1% tolerance, which may improve circuit performance in precision applications.

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