LM3671MFX-3.3 Equivalent & Substitute Parts

Part Overview

The LM3671MFX-3.3 is a buck switching regulator IC from Texas Instruments designed for positive fixed 3.3V output applications with 600mA current capacity. This device operates in the 2.7V to 5.5V input voltage range and features a 2MHz switching frequency with integrated synchronous rectification. The part is classified as obsolete, making equivalent and substitute parts necessary for new designs and ongoing production support.

Substiute Parts

LM3671MFX-3.3

Texas InstrumentsIn Stock: 1586LM3671MFX-3.3 Datasheet

Current PartRFQ

LM3671MFX-3.3/NOPB

Texas InstrumentsIn Stock: 41385LM3671MFX-3.3/NOPB Datasheet

DirectRFQ

ADP2108AUJZ-3.3-R7

Analog Devices Inc.In Stock: 12307ADP2108AUJZ-3.3-R7 Datasheet

MFR RecommendedRFQ

MCP1603T-330I/OS

Microchip TechnologyIn Stock: 34964MCP1603T-330I/OS Datasheet

MFR RecommendedRFQ

SC4626ZSKTRT

SemtechIn Stock: 9235SC4626ZSKTRT Datasheet

MFR RecommendedRFQ

Key Parameters

Substitute Part Grouping Explanation

Substitution eligibility for the LM3671MFX-3.3 is determined by the following core parameters:

• Output voltage: 3.3V fixed
• Output topology: Buck (step-down)
• Output configuration: Positive
• Number of outputs: Single output
• Package compatibility: SOT-23-5 form factor
• Synchronous rectification capability: Required
• Input voltage range: Minimum 2.7V, maximum 5.5V
• Mounting type: Surface mount

Substitute parts must maintain these electrical and mechanical specifications to ensure direct functional replacement without circuit redesign. Output current capacity and switching frequency may vary within acceptable design margins for the target application.

Parameter Comparison

Engineering Selection Recommendations

Primary Substitute: LM3671MFX-3.3/NOPB

The LM3671MFX-3.3/NOPB is the direct equivalent from Texas Instruments with identical electrical specifications and package format. This part is active in production and ROHS3 compliant, making it the preferred replacement for obsolete LM3671MFX-3.3 units. No circuit modifications are required for this substitution.

Secondary Substitute: ADP2108AUJZ-3.3-R7

The ADP2108AUJZ-3.3-R7 from Analog Devices Inc. meets all core substitution criteria with matching output voltage, topology, and package compatibility. This part offers extended operating temperature range (-40°C to 125°C) and lower minimum input voltage (2.3V). ROHS3 compliance and active production status support long-term availability.

Tertiary Substitute: MCP1603T-330I/OS

The MCP1603T-330I/OS from Microchip Technology provides functional equivalence with 500mA output current capacity. This part is suitable for applications where the full 600mA specification is not required. Extended operating temperature range and ROHS3 compliance are provided. Identical input voltage range and switching frequency match the original specification.

Alternative Substitute: SC4626ZSKTRT

The SC4626ZSKTRT from Semtech offers higher output current capacity (1A) with matching 3.3V output and SOT-23-5 package. This part is classified as not for new designs, limiting its suitability for new product development. Extended operating temperature range and RoHS compliance are available.

Frequently Asked Questions (FAQ)

Q: Can LM3671MFX-3.3/NOPB be used as a direct replacement for LM3671MFX-3.3?

A: Yes. The LM3671MFX-3.3/NOPB is electrically and mechanically identical to the obsolete LM3671MFX-3.3. No circuit modifications or PCB changes are required. The primary difference is product status (active vs. obsolete) and RoHS compliance.

Q: What is the difference between SOT-23-5 and TSOT-23-5 packages?

A: TSOT-23-5 is a thin variant of the SOT-23-5 package with reduced height. Both packages are mechanically compatible with standard SOT-23-5 PCB footprints. Verify PCB clearance specifications if height-sensitive applications are involved.

Q: Is the ADP2108AUJZ-3.3-R7 suitable for applications requiring 600mA output?

A: Yes. The ADP2108AUJZ-3.3-R7 provides 600mA output current capacity, matching the original LM3671MFX-3.3 specification. The lower minimum input voltage (2.3V vs. 2.7V) provides additional design flexibility.

Q: Why is MCP1603T-330I/OS rated for only 500mA when the original part provides 600mA?

A: The MCP1603T-330I/OS has a lower maximum output current specification (500mA). This part is suitable only for applications where the load current does not exceed 500mA. For designs requiring the full 600mA specification, use LM3671MFX-3.3/NOPB or ADP2108AUJZ-3.3-R7.

Q: What does "Not For New Designs" mean for the SC4626ZSKTRT?

A: This designation indicates the manufacturer does not recommend this part for new product development. While the part may be available in inventory, long-term supply and support are not guaranteed. Use this part only for legacy system maintenance or repair.

Q: Are all substitute parts RoHS compliant?

A: The LM3671MFX-3.3 is RoHS non-compliant. All recommended substitutes (LM3671MFX-3.3/NOPB, ADP2108AUJZ-3.3-R7, MCP1603T-330I/OS, and SC4626ZSKTRT) are RoHS compliant, supporting regulatory requirements for new designs.

Q: Can these parts be used interchangeably in existing designs?

A: Yes, provided the application requirements fall within the specified parameters of the substitute part. Verify output current requirements, input voltage range, and operating temperature range before selection. PCB footprint compatibility must be confirmed for TSOT-23-5 variants.