SPX3940T-L-3-3 Equivalent & Substitute Parts

Part Overview

The SPX3940T-L-3-3 is a linear voltage regulator IC from MaxLinear, Inc., designed to deliver a fixed 3.3V output at 1A in a TO-263-3 surface mount package. This part is discontinued at DiGi Electronics but remains available through inventory channels. Due to its discontinued status, equivalent substitute parts from active manufacturers are necessary for new designs and ongoing production requirements. Suitable alternatives maintain the same output voltage, package form factor, and core electrical characteristics while offering improved availability and extended product lifecycles.

Key Parameters

Parameter	Value
Manufacturer Part Number	SPX3940T-L-3-3
Manufacturer	MaxLinear, Inc.
Category	Power Management (PMIC)
Description	IC REG LINEAR 3.3V 1A TO263-3
Output Voltage (Fixed)	3.3V
Output Current	1A
Input Voltage (Max)	16V
Voltage Dropout (Max)	0.55V @ 1A
Package / Case	TO-263-3 (D2PAK, 3 Leads + Tab)
Mounting Type	Surface Mount
Operating Temperature	-40°C ~ 125°C
Protection Features	Over Current, Over Temperature, Reverse Polarity, Short Circuit, Transient Voltage
RoHS Status	RoHS Compliant
Product Status	Discontinued at DiGi Electronics

Substitute Part Grouping Explanation

Substitution eligibility for the SPX3940T-L-3-3 is determined by the following critical parameters:

Primary Substitution Criteria:

Fixed output voltage of 3.3V
TO-263-3 package compatibility (D2PAK form factor)
Surface mount technology
Operating temperature range of -40°C to 125°C
RoHS compliance status

Secondary Compatibility Factors:

Output current rating (1A minimum for direct replacement; higher ratings acceptable for design margin)
Input voltage maximum rating (16V or higher)
Voltage dropout characteristics at rated current
Protection feature set (Over Temperature and Short Circuit as minimum requirements)

Substitute parts are grouped into two categories based on output current capability: direct 1A replacements and higher-current alternatives (3A and 500mA variants) suitable for applications with different current requirements while maintaining identical package and voltage specifications.

Parameter Comparison

Parameter	SPX3940T-L-3-3	LM3940IS-3.3/NOPB	LM3940ISX-3.3/NOPB	MIC29310-3.3WU	MIC29310-3.3WU-TR	MIC5237-3.3YU	MIC5237-3.3YU-TR
Manufacturer	MaxLinear, Inc.	Texas Instruments	Texas Instruments	Microchip Technology	Microchip Technology	Microchip Technology	Microchip Technology
Output Voltage (Fixed)	3.3V	3.3V	3.3V	3.3V	3.3V	3.3V	3.3V
Output Current	1A	1A	1A	3A	3A	500mA	500mA
Input Voltage (Max)	16V	7.5V	7.5V	16V	16V	16V	16V
Voltage Dropout (Max)	0.55V @ 1A	0.2V @ 100mA	0.2V @ 100mA	1V @ 3A	1V @ 3A	0.7V @ 500mA	0.7V @ 500mA
Package / Case	TO-263-3	TO-263 (DDPAK-3)	TO-263 (DDPAK-3)	TO-263-3	TO-263-3	TO-263-3	TO-263-3
Operating Temperature	-40°C ~ 125°C	-40°C ~ 125°C	-40°C ~ 125°C	0°C ~ 125°C	0°C ~ 125°C	-40°C ~ 125°C	-40°C ~ 125°C
RoHS Status	RoHS Compliant	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant
Product Status	Discontinued	Active	Active	Active	Active	Active	Active
Moisture Sensitivity Level (MSL)	3 (168 Hours)	3 (168 Hours)	3 (168 Hours)	3 (168 Hours)	3 (168 Hours)	3 (168 Hours)	3 (168 Hours)

Engineering Selection Recommendations

Direct Replacement (1A Output Current):

LM3940IS-3.3/NOPB and LM3940ISX-3.3/NOPB from Texas Instruments are functionally equivalent to the SPX3940T-L-3-3 with identical 1A output current and TO-263 package compatibility. Both parts are in active production status with ROHS3 compliance. The LM3940ISX-3.3/NOPB variant is supplied in Cut Tape & Digi-Reel packaging, while LM3940IS-3.3/NOPB is supplied in Tube packaging. Selection between these two depends on assembly process requirements. Both offer superior voltage dropout performance (0.2V @ 100mA) compared to the original part. However, the input voltage maximum rating is limited to 7.5V, which is lower than the SPX3940T-L-3-3 specification of 16V. This limitation must be evaluated against actual circuit input voltage requirements.

Higher Current Alternative (3A Output Current):

MIC29310-3.3WU and MIC29310-3.3WU-TR from Microchip Technology provide 3A output current in the same TO-263-3 package with 16V input voltage rating matching the original part. These parts are suitable for applications requiring higher current capacity while maintaining identical package footprint and voltage specifications. Operating temperature range is 0°C to 125°C, which is narrower than the original part's -40°C to 125°C range. MIC29310-3.3WU-TR is supplied in Tape & Reel format for automated assembly, while MIC29310-3.3WU is supplied in Tube format.

Lower Current Alternative (500mA Output Current):

MIC5237-3.3YU and MIC5237-3.3YU-TR from Microchip Technology deliver 500mA output current in TO-263-3 packaging with full -40°C to 125°C operating temperature range and 16V input voltage rating. These parts are appropriate for applications with lower current requirements and offer improved PSRR performance (75dB @ 120Hz). MIC5237-3.3YU-TR is supplied in Tape & Reel format, while MIC5237-3.3YU is supplied in Tube format.

All substitute parts maintain RoHS compliance and identical MSL ratings. Selection should prioritize active production status and compliance certifications while confirming input voltage and operating temperature compatibility with specific application requirements.

Frequently Asked Questions (FAQ)

Q: Can I use LM3940IS-3.3/NOPB as a direct replacement for SPX3940T-L-3-3?

A: LM3940IS-3.3/NOPB is functionally compatible in terms of output voltage (3.3V), output current (1A), and package form factor (TO-263-3). However, the input voltage maximum rating differs: LM3940IS-3.3/NOPB is rated to 7.5V maximum input, while SPX3940T-L-3-3 is rated to 16V. Substitution is valid only if your circuit input voltage does not exceed 7.5V.

Q: What is the difference between MIC29310-3.3WU and MIC29310-3.3WU-TR?

A: Both parts are electrically identical with 3A output current and TO-263-3 package compatibility. The difference is packaging format: MIC29310-3.3WU is supplied in Tube packaging for manual assembly, while MIC29310-3.3WU-TR is supplied in Tape & Reel format for automated pick-and-place assembly. Select based on your manufacturing process requirements.

Q: Why would I choose MIC5237-3.3YU (500mA) over a 1A or 3A alternative?

A: MIC5237-3.3YU is appropriate when your application requires only 500mA or less output current. This part offers superior PSRR performance (75dB @ 120Hz) and maintains the full -40°C to 125°C operating temperature range of the original SPX3940T-L-3-3. Use this part when noise performance is a design consideration and current requirements are below 500mA.

Q: Are all substitute parts RoHS compliant?

A: Yes. All listed substitute parts carry ROHS3 compliance certification, meeting current environmental and regulatory requirements. The original SPX3940T-L-3-3 is RoHS Compliant. All parts share identical Moisture Sensitivity Level (MSL) ratings of 3 (168 Hours).

Q: What is the operating temperature range difference between substitutes?

A: SPX3940T-L-3-3, LM3940IS-3.3/NOPB, LM3940ISX-3.3/NOPB, MIC5237-3.3YU, and MIC5237-3.3YU-TR all operate across -40°C to 125°C. MIC29310-3.3WU and MIC29310-3.3WU-TR have a narrower range of 0°C to 125°C. Select the MIC29310 series only if your application does not require operation below 0°C.

Q: Can I use a higher current rated part (3A) in place of a 1A requirement?

A: Yes. A 3A-rated regulator can be used in applications designed for 1A output current. The higher current rating provides design margin and does not negatively affect circuit operation at lower current levels. MIC29310-3.3WU and MIC29310-3.3WU-TR are suitable for this purpose while maintaining TO-263-3 package compatibility.

Q: What packaging options are available for these substitutes?

A: Tube packaging is available for LM3940IS-3.3/NOPB, MIC29310-3.3WU, and MIC5237-3.3YU. Tape & Reel (TR) packaging is available for LM3940ISX-3.3/NOPB, MIC29310-3.3WU-TR, and MIC5237-3.3YU-TR. Select based on your assembly process: Tube for manual or semi-automated assembly, Tape & Reel for fully automated pick-and-place systems.

Request Quote (Ships tomorrow)

Part Number

Quantity

Company

Contact Name

E-mail

Message