LM3670MFX-1.8 Buck Switching Regulator Equivalent & Substitute Parts

Part Overview

The LM3670MFX-1.8 is a buck switching regulator IC manufactured by Texas Instruments, designed to deliver a fixed 1.8V output at 350mA from input voltages between 2.5V and 5.5V. This part is classified as obsolete, making equivalent and substitute parts necessary for new designs and production continuity. The device operates at 1MHz switching frequency with integrated synchronous rectification and is housed in a SC-74A/SOT-753 package suitable for surface mount applications.

Substiute Parts

LM3670MFX-1.8

Texas InstrumentsIn Stock: 6413LM3670MFX-1.8 Datasheet

Current PartRFQ

LM3670MFX-1.8/NOPB

Texas InstrumentsIn Stock: 844LM3670MFX-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 for the LM3670MFX-1.8 is determined by the following critical parameters:

• Output Voltage: Must be fixed at 1.8V
• Topology: Buck (step-down) switching regulator
• Output Configuration: Positive
• Package Compatibility: SC-74A/SOT-753 or SOT-23-5 variants (including thin TSOT-23-5)
• Input Voltage Range: Minimum 2.5V to 5.5V maximum
• Synchronous Rectification: Required
• Surface Mount: Required

Substitute parts are grouped into two categories:

1. Direct Equivalent (LM3670MFX-1.8/NOPB): Identical specifications with improved product status (Active) and RoHS3 compliance.

2. Functional Equivalents with Parameter Variations: Parts meeting core substitution criteria but with differences in output current capacity, switching frequency, or temperature range. These are suitable when the application can accommodate the parameter differences.

Parameter Comparison

Engineering Selection Recommendations

LM3670MFX-1.8/NOPB is the primary substitute for the obsolete LM3670MFX-1.8. It provides identical electrical and mechanical specifications with the advantage of active product status and RoHS3 compliance. This part is recommended for direct replacement in existing designs.

MAX1734EUK18+T is suitable for applications where output current requirements do not exceed 250mA. The minimum input voltage is 2.7V (versus 2.5V for the original), which may require verification in low-voltage applications. This part offers active status and RoHS3 compliance.

MCP1603T-180I/OS accommodates higher output current demands up to 500mA and features an extended operating temperature range to 125°C. The package variant is TSOT-23-5 (thin), which requires PCB layout verification for compatibility. RoHS3 compliant and active status.

RT8009-18GB and RT8009-18GJ5 provide the highest output current capacity at 600mA, suitable for applications requiring greater current delivery. Both variants are RoHS3 compliant and active. The RT8009-18GJ5 uses TSOT-23-5 packaging, while RT8009-18GB uses standard SC-74A/SOT-753. MSL rating is 3 (168 Hours) for both variants, requiring controlled storage conditions.

Frequently Asked Questions (FAQ)

Q: Can LM3670MFX-1.8/NOPB be used as a direct replacement for LM3670MFX-1.8?

A: Yes. The LM3670MFX-1.8/NOPB is electrically and mechanically identical to the original part. The primary differences are product status (Active versus Obsolete) and RoHS3 compliance. No circuit modifications are required.

Q: What is the difference between MAX1734EUK18+T and the original LM3670MFX-1.8?

A: The MAX1734EUK18+T has a lower maximum output current (250mA versus 350mA) and a higher minimum input voltage (2.7V versus 2.5V). It is suitable only for applications where the load current does not exceed 250mA and input voltage remains above 2.7V.

Q: Can MCP1603T-180I/OS be used in place of LM3670MFX-1.8?

A: Yes, with package verification. The MCP1603T-180I/OS meets all electrical requirements and provides higher output current (500mA). However, it uses TSOT-23-5 (thin) packaging instead of standard SOT-753. PCB layout and component placement must be verified for compatibility.

Q: What does MSL rating mean, and why do RT8009 parts have MSL 3?

A: MSL (Moisture Sensitivity Level) indicates how long a component can be stored in standard conditions before requiring baking. MSL 1 (Unlimited) allows indefinite storage. MSL 3 (168 Hours) requires baking if the component has been exposed to moisture for more than 168 hours. RT8009 parts require controlled storage and handling procedures.

Q: Are all substitute parts RoHS3 compliant?

A: Yes. All substitute parts listed are RoHS3 compliant. The original LM3670MFX-1.8 is non-compliant, making RoHS3-compliant substitutes necessary for applications requiring regulatory compliance.

Q: Which substitute part has the widest operating temperature range?

A: The MCP1603T-180I/OS operates from -40°C to 125°C (TJ), providing the widest temperature range. All other parts operate to 85°C maximum.

Q: Can RT8009-18GB and RT8009-18GJ5 be used interchangeably?

A: Both parts have identical electrical specifications and output current (600mA). The difference is packaging: RT8009-18GB uses SC-74A/SOT-753, while RT8009-18GJ5 uses TSOT-23-5 (thin). Selection depends on PCB layout requirements and available board space.