LM4128AMFX-3.3 Equivalent & Substitute Parts

Part Overview

The LM4128AMFX-3.3 is a Series Voltage Reference IC with fixed 3.3V output, ±0.1% tolerance, and 20 mA output current in SOT-23-5 surface mount packaging. This part is classified as obsolete, making equivalent and substitute parts necessary for new designs and ongoing production requirements. The LM4128AMFX-3.3 serves as a precision voltage reference in power management applications requiring stable output voltage with low noise characteristics.

Key Parameters

Parameter	Value
Output Voltage (Fixed)	3.3V
Output Current	20 mA
Tolerance	±0.1%
Temperature Coefficient	75 ppm/°C
Noise (0.1Hz to 10Hz)	310 µVp-p
Input Voltage Range	3.7V ~ 5.5V
Supply Current	100 µA
Operating Temperature	-40°C ~ 125°C (TJ)
Package	SOT-23-5 (SC-74A)
Mounting Type	Surface Mount

Substitute Part Grouping Explanation

Substitution for the LM4128AMFX-3.3 is determined by the following critical parameters:

Fixed output voltage of 3.3V
SOT-23-5 surface mount package compatibility
Operating temperature range of -40°C to 125°C
Input voltage range of 3.7V to 5.5V
Series voltage reference topology

Substitute parts are grouped into two categories:

Direct Equivalents (Texas Instruments LM4128 Series): Parts maintaining identical electrical specifications including 3.3V output, ±0.1% tolerance, 20 mA output current, and 75 ppm/°C temperature coefficient. These include LM4128AMFX-3.3/NOPB, LM4128AMF-3.3/NOPB, LM4128AQ1MF3.3/NOPB, and LM4128AQ1MFX3.3/NOPB.

Parametric Equivalents (Analog Devices MAX6037 Series): Parts with identical 3.3V output and SOT-23-5 packaging but differing in tolerance (±0.2% to ±0.3%), output current (5 mA), temperature coefficient (25 to 50 ppm/°C), and supply current (275 µA). These include MAX6037AAUK33+T and MAX6037BAUK33+T.

Parameter Comparison

Part Number	Manufacturer	Output Voltage	Output Current	Tolerance	Temp Coeff	Input Voltage	Supply Current	Package	Product Status	RoHS Status
LM4128AMFX-3.3	Texas Instruments	3.3V	20 mA	±0.1%	75 ppm/°C	3.7V ~ 5.5V	100 µA	SOT-23-5	Obsolete	Non-compliant
LM4128AMFX-3.3/NOPB	Texas Instruments	3.3V	20 mA	±0.1%	75 ppm/°C	3.7V ~ 5.5V	100 µA	SOT-23-5	Active	ROHS3 Compliant
LM4128AMF-3.3/NOPB	Texas Instruments	3.3V	20 mA	±0.1%	75 ppm/°C	3.7V ~ 5.5V	100 µA	SOT-23-5	Active	ROHS3 Compliant
LM4128AQ1MF3.3/NOPB	Texas Instruments	3.3V	20 mA	±0.1%	75 ppm/°C	3.7V ~ 5.5V	100 µA	SOT-23-5	Active	ROHS3 Compliant
LM4128AQ1MFX3.3/NOPB	Texas Instruments	3.3V	20 mA	±0.1%	75 ppm/°C	3.7V ~ 5.5V	100 µA	SOT-23-5	Active	ROHS3 Compliant
MAX6037AAUK33+T	Analog Devices Inc./Maxim Integrated	3.3V	5 mA	±0.2%	25 ppm/°C	4.6V ~ 5.5V	275 µA	SOT-23-5	Active	ROHS3 Compliant
MAX6037BAUK33+T	Analog Devices Inc./Maxim Integrated	3.3V	5 mA	±0.3%	50 ppm/°C	4.6V ~ 5.5V	275 µA	SOT-23-5	Active	ROHS3 Compliant

Engineering Selection Recommendations

For Direct Replacement: Select LM4128AMFX-3.3/NOPB, LM4128AMF-3.3/NOPB, LM4128AQ1MF3.3/NOPB, or LM4128AQ1MFX3.3/NOPB when the application requires identical electrical performance to the obsolete LM4128AMFX-3.3. All active variants maintain ±0.1% tolerance and 20 mA output current specifications. LM4128AQ1MF3.3/NOPB and LM4128AQ1MFX3.3/NOPB include automotive-grade qualification (AEC-Q100) and are suitable for automotive applications. All variants are ROHS3 compliant.

For Parametric Substitution: Select MAX6037AAUK33+T or MAX6037BAUK33+T when the application can accommodate reduced output current (5 mA versus 20 mA), relaxed tolerance specifications (±0.2% to ±0.3% versus ±0.1%), and increased supply current (275 µA versus 100 µA). These parts offer superior temperature coefficient performance (25 to 50 ppm/°C versus 75 ppm/°C) and lower noise characteristics. Both are active products with ROHS3 compliance.

Packaging Considerations: All substitute parts maintain SOT-23-5 surface mount packaging, ensuring mechanical and thermal compatibility with existing PCB layouts. Tape & Reel (TR) and Cut Tape (CT) packaging options are available across the substitute lineup.

Frequently Asked Questions (FAQ)

Q: Can LM4128AMFX-3.3/NOPB directly replace the obsolete LM4128AMFX-3.3?

A: Yes. LM4128AMFX-3.3/NOPB is electrically and mechanically identical to the obsolete part, with the primary difference being active product status and ROHS3 compliance. No circuit modifications are required.

Q: What is the difference between LM4128AMF-3.3/NOPB and LM4128AMFX-3.3/NOPB?

A: Both parts maintain identical electrical specifications (3.3V output, ±0.1% tolerance, 20 mA output current). The primary difference is packaging format: LM4128AMF-3.3/NOPB is supplied in Tape & Reel, while LM4128AMFX-3.3/NOPB is also available in Tape & Reel. Selection depends on procurement and assembly requirements.

Q: Are automotive-qualified variants available?

A: Yes. LM4128AQ1MF3.3/NOPB and LM4128AQ1MFX3.3/NOPB are automotive-grade parts with AEC-Q100 qualification, maintaining identical electrical specifications to standard variants. These are suitable for automotive applications requiring qualified components.

Q: Can MAX6037AAUK33+T replace LM4128AMFX-3.3 in all applications?

A: MAX6037AAUK33+T is a parametric equivalent with 3.3V output and SOT-23-5 packaging. However, it differs in output current (5 mA versus 20 mA), tolerance (±0.2% versus ±0.1%), and temperature coefficient (25 ppm/°C versus 75 ppm/°C). Substitution is valid only when the application can operate within these relaxed specifications and reduced output current requirements.

Q: What is the inventory status of substitute parts?

A: LM4128AQ1MF3.3/NOPB has the highest inventory availability at 40,050 pieces. LM4128AMF-3.3/NOPB and LM4128AMFX-3.3/NOPB have 4,359 and 4,206 pieces respectively. MAX6037AAUK33+T has 3,491 pieces, while MAX6037BAUK33+T has 993 pieces.

Q: Are all substitute parts ROHS3 compliant?

A: Yes. All active substitute parts listed (LM4128 and MAX6037 series) are ROHS3 compliant. The original obsolete LM4128AMFX-3.3 is non-compliant.

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