LM3670MF-3.3 Equivalent & Substitute Parts

Part Overview

The LM3670MF-3.3 is a buck switching regulator IC manufactured by Texas Instruments, designed to deliver a fixed 3.3V output at 350mA from an input voltage range of 2.5V to 5.5V. This component operates at 1MHz switching frequency with integrated synchronous rectification and is packaged in SC-74A (SOT-753) form factor.

The LM3670MF-3.3 has reached obsolete product status. Equivalent and substitute parts are necessary to maintain design continuity and ensure component availability for new production runs and legacy system support.

Substiute Parts

LM3670MF-3.3

Texas InstrumentsIn Stock: 1190LM3670MF-3.3 Datasheet

Current PartRFQ

LM3670MF-3.3/NOPB

Texas InstrumentsIn Stock: 9394LM3670MF-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

RT8008-12GB

Richtek USA Inc.In Stock: 8300RT8008-12GB Datasheet

MFR RecommendedRFQ

RT8009-33GB

Richtek USA Inc.In Stock: 6411RT8009-33GB Datasheet

MFR RecommendedRFQ

RT8009-33GJ5

Richtek USA Inc.In Stock: 15251RT8009-33GJ5 Datasheet

MFR RecommendedRFQ

SC4626ZSKTRT

SemtechIn Stock: 9235SC4626ZSKTRT Datasheet

MFR RecommendedRFQ

Key Parameters

Substitute Part Grouping Explanation

Substitution eligibility for the LM3670MF-3.3 is determined by the following critical parameters:

Primary Substitution Criteria:

• Output voltage: 3.3V fixed
• Input voltage range: Minimum 2.5V, maximum 5.5V
• Output current capability: Minimum 350mA
• Topology: Buck switching regulator
• Output configuration: Positive
• Synchronous rectification: Yes
• Package compatibility: SOT-23-5 form factor (SC-74A or TSOT-23-5 variants)
• Mounting type: Surface mount

Secondary Compatibility Factors:

• Operating temperature range: -40°C minimum, 85°C or higher maximum
• RoHS compliance status
• Moisture sensitivity level
• Switching frequency (operational range, not critical for substitution)

Substitute parts are grouped into two categories:

Direct Equivalents: Parts with identical or superior electrical specifications and active product status, suitable for direct replacement without circuit modification.

Functional Equivalents: Parts meeting all primary substitution criteria with enhanced performance characteristics (higher output current, extended temperature range, improved switching frequency) that maintain backward compatibility.

Parameter Comparison

Engineering Selection Recommendations

Recommended Primary Substitute: LM3670MF-3.3/NOPB

The LM3670MF-3.3/NOPB is the direct equivalent manufactured by Texas Instruments with identical electrical specifications and package configuration. This part maintains active product status and achieves ROHS3 compliance, addressing the RoHS non-compliance limitation of the obsolete LM3670MF-3.3. This is the preferred choice for direct replacement in existing designs.

Recommended Secondary Substitutes for Enhanced Performance:

ADP2108AUJZ-3.3-R7 (Analog Devices Inc.) provides 600mA output current capacity with extended operating temperature range to 125°C and lower minimum input voltage (2.3V). This part is suitable for applications requiring higher current delivery or wider temperature operating margins.

MCP1603T-330I/OS (Microchip Technology) delivers 500mA output current with 125°C maximum operating temperature and ROHS3 compliance. This part offers a balanced performance upgrade with extended thermal specifications.

RT8009-33GJ5 (Richtek USA Inc.) provides 600mA output current in TSOT-23-5 thin package format with active product status and ROHS3 compliance. This part is suitable for space-constrained applications requiring higher current capacity.

Alternative for Maximum Current Capacity: SC4626ZSKTRT

SC4626ZSKTRT (Semtech) delivers 1A output current with extended operating temperature to 125°C. This part is designated "Not For New Designs" but remains available for legacy system support and applications requiring maximum current delivery within the 3.3V output specification.

Compliance Considerations:

All recommended active substitutes achieve ROHS3 compliance, addressing regulatory requirements not met by the obsolete LM3670MF-3.3. Selection should prioritize parts with active product status for long-term supply chain stability.

Frequently Asked Questions (FAQ)

Q: Can LM3670MF-3.3/NOPB be used as a direct replacement for LM3670MF-3.3?

A: Yes. LM3670MF-3.3/NOPB is the direct equivalent with identical electrical specifications, package configuration, and functional performance. The primary difference is active product status and ROHS3 compliance. No circuit modifications are required.

Q: What is the difference between SC-74A and TSOT-23-5 packages?

A: Both are SOT-23-5 form factors with identical pin configurations and footprints. SC-74A is the standard thickness variant, while TSOT-23-5 is the thin variant. They are mechanically and electrically compatible for PCB assembly purposes.

Q: Can I use ADP2108AUJZ-3.3-R7 if my circuit is designed for 350mA output?

A: Yes. ADP2108AUJZ-3.3-R7 provides 600mA output current capacity, which exceeds the 350mA requirement. The higher current rating does not affect circuit operation at lower current levels. The part is fully backward compatible.

Q: What does MSL 3 (168 Hours) mean for RT8009-33GJ5?

A: MSL 3 indicates Moisture Sensitivity Level 3, requiring component storage in controlled humidity conditions with a maximum floor life of 168 hours after moisture barrier bag opening. This requires more stringent handling procedures compared to MSL 1 (unlimited) parts.

Q: Is SC4626ZSKTRT suitable for new designs?

A: SC4626ZSKTRT is designated "Not For New Designs" by the manufacturer. It remains available for legacy system support and replacement applications but should not be selected for new product development. Use LM3670MF-3.3/NOPB, ADP2108AUJZ-3.3-R7, MCP1603T-330I/OS, or RT8009-33GJ5 for new designs.

Q: Do all substitute parts support the 2.5V to 5.5V input voltage range?

A: All recommended substitutes support the 5.5V maximum input voltage. MCP1603T-330I/OS has a 2.7V minimum input voltage (versus 2.5V for others), which may affect operation in applications with input voltages between 2.5V and 2.7V. ADP2108AUJZ-3.3-R7 supports 2.3V minimum input voltage, providing extended low-voltage operation capability.

Q: What is the impact of switching frequency differences on circuit design?

A: Switching frequency differences (1MHz to 3MHz across substitutes) affect output filter component selection and EMI characteristics but do not prevent functional substitution. Higher switching frequencies allow smaller filter inductors and capacitors. Circuit validation is recommended when switching frequency differs significantly from the original design specification.