LM3671MFX-1.5 Equivalent & Substitute Parts

Part Overview

The LM3671MFX-1.5 is a buck switching regulator IC from Texas Instruments, designed for positive fixed 1.5V output applications with 600mA current capacity. This component operates across a 2.7V to 5.5V input range and features a 2MHz switching frequency with integrated synchronous rectification in a compact SC-74A (SOT-753) surface mount package.

The LM3671MFX-1.5 is classified as obsolete. Identifying equivalent and substitute parts is necessary to ensure design continuity, maintain supply chain reliability, and support ongoing production requirements for applications currently utilizing this regulator.

Substiute Parts

LM3671MFX-1.5

Texas InstrumentsIn Stock: 2203LM3671MFX-1.5 Datasheet

Current PartRFQ

LM3674MF-1.5/NOPB

Texas InstrumentsIn Stock: 1128LM3674MF-1.5/NOPB Datasheet

DirectRFQ

ADP2108AUJZ-1.5-R7

Analog Devices Inc.In Stock: 3539ADP2108AUJZ-1.5-R7 Datasheet

MFR RecommendedRFQ

MCP1603T-150I/OS

Microchip TechnologyIn Stock: 1136MCP1603T-150I/OS Datasheet

MFR RecommendedRFQ

Key Parameters

Substitute Part Grouping Explanation

Substitution eligibility for the LM3671MFX-1.5 is determined by the following critical parameters:

• Output Voltage: Must be fixed at 1.5V
• Output Current: Minimum 600mA (equal or greater capacity acceptable)
• Input Voltage Range: Must accommodate 2.7V to 5.5V minimum
• Topology: Buck (step-down) switching regulator
• Package: SC-74A or SOT-23-5 variants (surface mount, pin-compatible)
• Synchronous Rectification: Must be present
• Output Configuration: Positive fixed output

Three substitute parts meet these criteria:

1. LM3674MF-1.5/NOPB (Texas Instruments) – Direct manufacturer alternative with active product status
2. ADP2108AUJZ-1.5-R7 (Analog Devices Inc.) – Manufacturer-recommended substitute with extended temperature range
3. MCP1603T-150I/OS (Microchip Technology) – Manufacturer-recommended substitute with reduced output current specification

Parameter Comparison

Engineering Selection Recommendations

LM3674MF-1.5/NOPB is the primary direct substitute. It maintains identical electrical specifications (600mA output, 2MHz switching frequency, 1.5V fixed output) and package compatibility with the obsolete LM3671MFX-1.5. The LM3674MF-1.5/NOPB carries active product status and RoHS3 compliance, providing long-term supply assurance. The only operational difference is a narrower operating temperature range (-30°C to 85°C versus -40°C to 85°C); this is acceptable for applications not requiring the full -40°C minimum specification.

ADP2108AUJZ-1.5-R7 is a manufacturer-recommended alternative from Analog Devices Inc. It provides identical 600mA output current and 1.5V fixed output voltage. The ADP2108AUJZ-1.5-R7 offers an extended operating temperature range (-40°C to 125°C) and lower minimum input voltage (2.3V versus 2.7V), making it suitable for applications requiring broader thermal or input voltage specifications. The switching frequency is 3MHz, which may affect PCB layout and filtering considerations. Package compatibility is maintained through SOT-23-5 Thin (TSOT-23-5) pinout equivalence.

MCP1603T-150I/OS is a manufacturer-recommended alternative from Microchip Technology. It meets the 1.5V fixed output and 2MHz switching frequency requirements. The output current specification is 500mA, which is 100mA below the original 600mA rating. This part is suitable only for applications where the actual load current does not exceed 500mA. The MCP1603T-150I/OS provides extended operating temperature range (-40°C to 125°C) and maintains SOT-23-5 Thin package compatibility.

All three substitutes carry RoHS3 compliance and REACH Unaffected status, supporting modern regulatory requirements.

Frequently Asked Questions (FAQ)

Q: Can the LM3674MF-1.5/NOPB directly replace the LM3671MFX-1.5 without PCB modifications?

A: Yes. The LM3674MF-1.5/NOPB maintains identical electrical specifications and SC-74A (SOT-753) package pinout. No PCB layout changes are required. The narrower operating temperature range (-30°C to 85°C) must be verified against application requirements.

Q: What is the key difference between the ADP2108AUJZ-1.5-R7 and the original LM3671MFX-1.5?

A: The ADP2108AUJZ-1.5-R7 operates at 3MHz switching frequency compared to 2MHz in the LM3671MFX-1.5. This higher frequency may reduce output filter component size but requires verification of PCB layout compatibility. The ADP2108AUJZ-1.5-R7 also accepts lower minimum input voltage (2.3V) and operates across a wider temperature range (-40°C to 125°C).

Q: Is the MCP1603T-150I/OS suitable as a direct replacement?

A: The MCP1603T-150I/OS is suitable only if the application load current does not exceed 500mA. The original LM3671MFX-1.5 is rated for 600mA output. Applications requiring the full 600mA specification must use either the LM3674MF-1.5/NOPB or ADP2108AUJZ-1.5-R7.

Q: Are all substitute parts RoHS compliant?

A: The LM3671MFX-1.5 is RoHS non-compliant. All three substitute parts (LM3674MF-1.5/NOPB, ADP2108AUJZ-1.5-R7, and MCP1603T-150I/OS) are RoHS3 compliant, supporting modern manufacturing and environmental regulations.

Q: What package considerations apply to the Analog Devices and Microchip alternatives?

A: The ADP2108AUJZ-1.5-R7 and MCP1603T-150I/OS use SOT-23-5 Thin (TSOT-23-5) packaging, which is physically compatible with the original SC-74A (SOT-753) pinout. Pin assignments are equivalent, but the thin variant may have different height specifications. PCB footprint verification is recommended before production implementation.

Q: Which substitute offers the best long-term availability?

A: The LM3674MF-1.5/NOPB is the recommended choice for long-term supply continuity. It is manufactured by the same company as the original part, carries active product status, and maintains identical electrical and package specifications. Current inventory levels (1101 pcs) support immediate procurement.