LM3671MFX-1.8 Equivalent & Substitute Parts

Part Overview

The LM3671MFX-1.8 is a buck switching regulator IC from Texas Instruments designed for positive fixed 1.8V output applications. This device delivers 600mA output current with a 2MHz switching frequency and integrated synchronous rectification. The part is classified as obsolete, making equivalent and substitute parts necessary for new designs and ongoing production requirements. Active alternatives from Texas Instruments and other manufacturers provide direct functional replacement with improved product status and compliance certifications.

Substiute Parts

LM3671MFX-1.8

Texas InstrumentsIn Stock: 17534LM3671MFX-1.8 Datasheet

Current PartRFQ

LM3671MFX-1.8/NOPB

Texas InstrumentsIn Stock: 17223LM3671MFX-1.8/NOPB Datasheet

DirectRFQ

LM3674MF-1.8/NOPB

Texas InstrumentsIn Stock: 2914LM3674MF-1.8/NOPB Datasheet

DirectRFQ

LM3674MFX-1.8/NOPB

Texas InstrumentsIn Stock: 1168LM3674MFX-1.8/NOPB Datasheet

DirectRFQ

MAX1734EUK18+T

Analog Devices Inc./Maxim IntegratedIn Stock: 12414MAX1734EUK18+T Datasheet

MFR RecommendedRFQ

MCP1603T-180I/OS

Microchip TechnologyIn Stock: 15651MCP1603T-180I/OS Datasheet

MFR RecommendedRFQ

Key Parameters

Substitute Part Grouping Explanation

Substitution for the LM3671MFX-1.8 is determined by the following critical parameters: fixed 1.8V output voltage, buck topology with synchronous rectification, input voltage range of 2.7V to 5.5V, SOT-23-5 package compatibility, and surface mount configuration. Output current capacity and switching frequency are secondary considerations that may vary within acceptable design margins.

Substitute parts are grouped into two categories:

Direct Texas Instruments Equivalents: LM3671MFX-1.8/NOPB, LM3674MF-1.8/NOPB, and LM3674MFX-1.8/NOPB maintain identical electrical specifications and package form factors. These parts share the same input/output voltage parameters, switching frequency, and thermal characteristics. The primary differences are product status (active vs. obsolete) and RoHS compliance certifications.

Cross-Manufacturer Alternatives: MAX1734EUK18+T (Analog Devices Inc./Maxim Integrated) and MCP1603T-180I/OS (Microchip Technology) provide functional equivalence with variations in output current capacity and switching frequency. These parts maintain the critical 1.8V fixed output, 2.7V to 5.5V input range, SOT-23-5 package, and synchronous rectification topology.

Parameter Comparison

Engineering Selection Recommendations

Primary Recommendation: LM3671MFX-1.8/NOPB or LM3674MFX-1.8/NOPB are the preferred substitutes. Both parts are active products with ROHS3 compliance certification and maintain identical electrical specifications to the obsolete LM3671MFX-1.8. LM3671MFX-1.8/NOPB is available in Cut Tape and Digi-Reel packaging, while LM3674MFX-1.8/NOPB is supplied in Tape & Reel format. The LM3674 series operates at a minimum temperature of -30°C compared to -40°C for the LM3671, which may be a consideration for extended temperature range applications.

Secondary Recommendation: MCP1603T-180I/OS from Microchip Technology provides functional equivalence with 500mA output current capacity and extended operating temperature range to 125°C. This part is suitable for applications where the 600mA specification is not critical and higher temperature performance is beneficial. The TSOT-23-5 package is mechanically compatible with standard SOT-23-5 footprints.

Alternative Consideration: MAX1734EUK18+T from Analog Devices Inc./Maxim Integrated is suitable only for applications requiring 250mA or less output current. The reduced current capacity and lower switching frequency (1.2MHz) make this part applicable only to specific low-power designs.

Frequently Asked Questions (FAQ)

Q: Can LM3674MF-1.8/NOPB directly replace LM3671MFX-1.8 in existing designs?

A: Yes. Both parts share identical input voltage range (2.7V to 5.5V), fixed 1.8V output, 600mA output current, 2MHz switching frequency, and SOT-23-5 package. The LM3674 operates at a minimum temperature of -30°C versus -40°C for the LM3671. Verify your application's minimum operating temperature requirement before substitution.

Q: What is the difference between LM3674MF-1.8/NOPB and LM3674MFX-1.8/NOPB?

A: Both parts are electrically identical with the same specifications and active product status. The primary difference is packaging format: LM3674MF-1.8/NOPB is supplied in Tape & Reel, while LM3674MFX-1.8/NOPB is also supplied in Tape & Reel. Inventory levels differ between the two variants.

Q: Is MCP1603T-180I/OS a suitable replacement for 600mA applications?

A: MCP1603T-180I/OS is rated for 500mA output current, which is below the 600mA specification of the LM3671MFX-1.8. This part is suitable only for applications where the load current does not exceed 500mA. The TSOT-23-5 package is mechanically compatible with standard SOT-23-5 footprints.

Q: Why is MAX1734EUK18+T listed as a substitute if it only provides 250mA?

A: MAX1734EUK18+T maintains the critical electrical parameters: 1.8V fixed output, 2.7V to 5.5V input range, buck topology with synchronous rectification, and SOT-23-5 package. This part is applicable only to designs requiring 250mA or less output current.

Q: Are all substitute parts RoHS compliant?

A: Yes. All active substitute parts (LM3671MFX-1.8/NOPB, LM3674MF-1.8/NOPB, LM3674MFX-1.8/NOPB, MAX1734EUK18+T, and MCP1603T-180I/OS) are ROHS3 compliant. The original LM3671MFX-1.8 is RoHS non-compliant.

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. MCP1603T-180I/OS uses the TSOT-23-5 package while other substitutes use standard SOT-23-5.

Q: Can I use these substitutes interchangeably in production?

A: Direct Texas Instruments substitutes (LM3671MFX-1.8/NOPB, LM3674MF-1.8/NOPB, LM3674MFX-1.8/NOPB) are interchangeable for identical electrical requirements. Cross-manufacturer alternatives (MAX1734EUK18+T, MCP1603T-180I/OS) require design verification based on output current capacity and thermal performance differences.