LM3674MFX-1.8 Buck Switching Regulator Equivalent & Substitute Parts

Part Overview

The LM3674MFX-1.8 is a buck switching regulator IC manufactured by Texas Instruments, designed for positive fixed 1.8V output applications with 600mA current capacity. This part operates across an input voltage range of 2.7V to 5.5V and features a 2MHz switching frequency with integrated synchronous rectification in a compact SC-74A (SOT-753) surface mount package.

The LM3674MFX-1.8 is classified as obsolete. Equivalent and substitute parts are necessary to ensure design continuity, maintain supply chain reliability, and support ongoing production requirements for applications currently utilizing this regulator.

Substiute Parts

LM3674MFX-1.8

Texas InstrumentsIn Stock: 2214LM3674MFX-1.8 Datasheet

Current PartRFQ

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

RT8009-18GB

Richtek USA Inc.In Stock: 3099RT8009-18GB Datasheet

MFR RecommendedRFQ

RT8009-18GJ5

Richtek USA Inc.In Stock: 7357RT8009-18GJ5 Datasheet

MFR RecommendedRFQ

Key Parameters

Substitute Part Grouping Explanation

Substitution of the LM3674MFX-1.8 is determined by the following critical parameters:

• Output voltage specification: 1.8V fixed
• Input voltage range compatibility: 2.7V to 5.5V minimum
• Output current capacity: 600mA or greater
• Topology: Buck switching regulator
• Synchronous rectification: Required
• Package compatibility: SC-74A (SOT-753) or TSOT-23-5 (pin-compatible variants)
• Mounting type: Surface mount

Substitute parts must maintain electrical equivalence across these parameters. Package variants (SOT-23-5 vs. TSOT-23-5) are considered compatible due to identical pinout and footprint compatibility. Output current ratings equal to or exceeding 600mA satisfy the current requirement. Switching frequency variations are acceptable provided all other electrical specifications align.

Parameter Comparison

Engineering Selection Recommendations

Direct Equivalent (Highest Compatibility): LM3674MFX-1.8/NOPB is the direct equivalent of the obsolete LM3674MFX-1.8. This part maintains identical electrical specifications, package configuration, and pinout. The primary distinction is product status (Active vs. Obsolete) and RoHS compliance (ROHS3 Compliant). This part is the preferred replacement for direct substitution in existing designs.

Full-Specification Alternatives (600mA Output Current): RT8009-18GB and RT8009-18GJ5 (Richtek USA Inc.) provide complete electrical equivalence with 600mA output current matching the original specification. Both variants maintain the 1.8V fixed output, 2MHz-equivalent switching performance (1.25MHz actual), and synchronous rectification. RT8009-18GB uses SC-74A packaging; RT8009-18GJ5 uses TSOT-23-5 packaging. Both are ROHS3 compliant and carry active product status.

Reduced-Current Alternative (250mA Output): MAX1734EUK18+T (Analog Devices Inc./Maxim Integrated) is suitable only for applications requiring 250mA or less output current. This part maintains 1.8V output, 2.7V–5.5V input range, and synchronous rectification. The reduced current capacity and lower switching frequency (1.2MHz) make this option applicable only to lower-power designs.

Moderate-Current Alternative (500mA Output): MCP1603T-180I/OS (Microchip Technology) provides 500mA output current, suitable for applications requiring less than 600mA. This part maintains 1.8V output, 2MHz switching frequency, and synchronous rectification. Extended operating temperature range (-40°C to 125°C TJ) provides thermal margin. TSOT-23-5 packaging requires PCB layout verification for compatibility with SC-74A footprints.

All substitute parts maintain REACH compliance and EAR99 export classification consistent with the original part.

Frequently Asked Questions (FAQ)

Q: Can MAX1734EUK18+T replace LM3674MFX-1.8 in all applications? A: No. MAX1734EUK18+T is limited to 250mA output current, compared to the original 600mA specification. Use this part only in designs requiring 250mA or less. For applications requiring the full 600mA capacity, select LM3674MFX-1.8/NOPB, RT8009-18GB, or RT8009-18GJ5.

Q: Are TSOT-23-5 and SC-74A packages interchangeable? A: TSOT-23-5 and SC-74A packages share identical pinout and are footprint-compatible on PCBs designed for either package type. However, verify your PCB layout supports the specific package variant before substitution. MCP1603T-180I/OS and RT8009-18GJ5 use TSOT-23-5; LM3674MFX-1.8/NOPB and RT8009-18GB use SC-74A.

Q: What is the difference between LM3674MFX-1.8 and LM3674MFX-1.8/NOPB? A: Both parts are electrically identical with matching specifications and pinout. The primary differences are product status (Obsolete vs. Active) and RoHS compliance (Non-Compliant vs. ROHS3 Compliant). LM3674MFX-1.8/NOPB is the active production equivalent.

Q: Can I use RT8009-18GB or RT8009-18GJ5 as direct replacements? A: Yes, both Richtek parts provide full electrical equivalence with 600mA output current. RT8009-18GB uses SC-74A packaging; RT8009-18GJ5 uses TSOT-23-5 packaging. Select based on your PCB layout requirements. Both are ROHS3 compliant and actively produced.

Q: Does switching frequency variation affect circuit performance? A: Switching frequency differences (1.2MHz to 2MHz) may affect output ripple, EMI characteristics, and component selection for external filtering. Designs optimized for 2MHz operation (LM3674MFX-1.8, MCP1603T-180I/OS) maintain closest performance alignment. Lower-frequency alternatives (MAX1734EUK18+T at 1.2MHz, RT8009 variants at 1.25MHz) require verification of filter component compatibility.

Q: Are all substitute parts RoHS compliant? A: All active substitute parts listed (LM3674MFX-1.8/NOPB, MAX1734EUK18+T, MCP1603T-180I/OS, RT8009-18GB, RT8009-18GJ5) are ROHS3 compliant. The original LM3674MFX-1.8 is RoHS non-compliant due to its obsolete status.

Q: Which substitute part has the widest operating temperature range? A: MCP1603T-180I/OS operates across -40°C to 125°C (TJ), providing the widest temperature margin. Other parts operate to -40°C or -30°C maximum, with upper limits of 85°C (TA). Select based on your application's thermal requirements.