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Texas Instruments LM3674MF-ADJ
- Part No.:
- LM3674MF-ADJ
- Manufacturer:
- Texas Instruments
- Package:
- SC-74A, SOT-753
- Datasheet:
-
LM3674MF-ADJ.pdf
- Description:
- IC REG BUCK ADJ 600MA SOT23-5
- Quantity:
- Payment:
- Shipping:
Inventory:4,132
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Product details
Overview
LM3674MF-ADJ from Texas Instruments is a 2-MHz, 600-mA synchronous step-down DC-DC converter in SOT-23-5 package, designed to regulate output voltage from 1 V to 3.3 V using an external resistor divider. It operates from a single Li-Ion cell (2.7 V to 5.5 V input), delivers up to 600 mA load current, features internal soft-start and 0.01 µA shutdown current, and targets power management in space-constrained portable electronics.
For engineers reviewing the LM3674MF-ADJ datasheet, LM3674MF-ADJ pinout, LM3674MF-ADJ application, or LM3674MF-ADJ equivalent, key selection considerations include adjustable output via FB pin feedback (VFB = 0.5 V), 2-MHz fixed-frequency PWM operation, internal synchronous rectification for >90% efficiency at mid-load, and thermal/overcurrent protection - all in a 2.90 mm × 1.60 mm SOT-23 footprint.
Technical Context
The LM3674MF-ADJ employs voltage-mode PWM control with input voltage feed-forward to maintain stable regulation across line and load variations. Its internal 0.5-V reference connects to the FB pin, enabling precise output setting via R1/R2 divider; the device disables internal fixed-voltage dividers when configured as adjustable.
During operation, the PFET switch (RDS(ON) = 380–500 mΩ) and NFET synchronous rectifier (RDS(ON) = 250–400 mΩ) alternate at 2 MHz (1.6–2.6 MHz over temperature), delivering regulated output while minimizing external component count - only VIN, SW, FB, EN, and GND pins require connection to support full functionality with CIN, COUT, and L1.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Input Voltage Range | 2.7 V to 5.5 V - supports direct operation from single Li-Ion battery without pre-regulation. |
| Output Current | 600 mA maximum - sufficient for core logic rails in mobile SoCs and baseband processors. |
| Switching Frequency | 2 MHz typical - enables use of small 2.2-µH inductors and 10-µF ceramic output capacitors. |
| Feedback Reference | 0.5 V - sets output voltage via external resistor divider (VOUT = 0.5 × (1 + R1/R2)). |
| Shutdown Current | 0.01 µA typical - preserves battery life during system sleep modes in portable devices. |
| Thermal Protection | Integrated thermal shutdown - disables switching above 125°C junction temperature to prevent damage. |
| Current Limit | 1020 mA typical peak - protects internal switches and external inductor during overload or short-circuit events. |
Pinout & Package
SOT-23-5 package (2.90 mm × 1.60 mm body size) with exposed pad not electrically connected; requires standard SMT reflow profile per JEDEC J-STD-020.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| VIN (Pin 1) | Power input | Connects to input filter capacitor (CIN = 4.7 µF); must be ≥2.7 V for enable and regulation. |
| GND (Pin 2) | Ground reference | Common return path for input/output circuits and internal control logic; ties to PCB ground plane. |
| EN (Pin 3) | Enable control | Logic-high (>1 V) enables regulation; <0.4 V forces shutdown (0.01 µA ISHDN); must not float. |
| FB (Pin 4) | Feedback input | Analog input sensing output voltage via R1/R2 divider; regulates to 0.5 V - determines VOUT. |
| SW (Pin 5) | Switching node | Connects to inductor (L1 = 2.2 µH); carries high di/dt pulses - requires tight layout to minimize EMI. |
Key Features
| Feature | Design Value |
|---|---|
| Internal synchronous rectification | Replaces external Schottky diode - reduces conduction loss and improves efficiency by 8–12% at 300 mA. |
| 2-MHz fixed-frequency PWM | Enables compact BOM: eliminates need for large LC filters; supports 0805-size 10-µF X5R output capacitors. |
| Programmable output (1 V to 3.3 V) | Set via external R1/R2 divider on FB pin - avoids inventory duplication across multiple fixed-output variants. |
| Integrated soft-start | Ramps switch current limit in steps (70/140/280/1020 mA) - limits inrush current into output capacitance during startup. |
| Low-dropout (100% duty-cycle) mode | PFET fully on when VIN ≈ VOUT - maintains regulation down to VIN,MIN = VOUT + ILOAD × (RDS(ON) + RL). |
Applications
| Mobile Phone Core Rail | MP3 Player Audio Codec Supply |
|---|---|
|
Use Scenario: Powers ARM-based application processor core (1.2 V @ 500 mA) from single-cell Li-Ion battery during active playback and UI navigation. IC Role / Device Role / Timing Role: Primary buck regulator providing tightly regulated, low-noise core voltage with fast transient response to CPU load changes. Use Value: 2-MHz switching minimizes output ripple (<25 mV p-p) and enables use of tiny 2.2-µH shielded inductor - critical for thin handset form factor. |
Use Scenario: Supplies 1.8 V to stereo audio DAC/ADC in flash-based MP3 player with 8-hour battery life target. IC Role / Device Role / Timing Role: Efficient intermediate rail generator converting 3.6 V battery to clean 1.8 V analog supply, synchronized to system clock domain. Use Value: 0.01 µA shutdown current extends standby time; internal soft-start prevents pop/click during power-on sequencing. |
| Portable Hard Disk Drive Motor Driver | Digital Still Camera Image Sensor Bias |
|
Use Scenario: Provides 3.3 V motor drive rail for 1.8-inch HDD spindle and voice coil actuator in ultra-portable notebook. IC Role / Device Role / Timing Role: High-current (600 mA) buck stage delivering stable voltage under dynamic mechanical load transients. Use Value: Thermal shutdown and cycle-by-cycle current limiting protect against stall-induced overtemperature and inductor saturation. |
Use Scenario: Generates 2.8 V bias for CMOS image sensor analog front-end in compact digital camera with auto-focus and flash. IC Role / Device Role / Timing Role: Low-noise adjustable supply ensuring consistent pixel response and minimal fixed-pattern noise. Use Value: Adjustable output allows fine-tuning to sensor datasheet VANA tolerance (±2%); 0.5-V FB reference enables <1% output accuracy with 1% resistors. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar step-down DC-DC converter applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| TPS62231DRYR | 2.25-MHz switching, 600-mA output, 0.6-V reference, integrated compensation - smaller 1.2-mm × 1.6-mm DSBGA package. | Requires different feedback network design due to lower reference voltage; optimized for ultra-thin wearables. | Select when board area is constrained and 0.6-V reference simplifies resistor selection for sub-1.2-V outputs. |
| AP3012KTR-G1 | 1.5-MHz switching, 600-mA output, 1.25-V reference, no internal synchronous rectifier - requires external Schottky diode. | Lower efficiency (~82% at 300 mA vs 92% for LM3674MF-ADJ); higher thermal dissipation in same SOT-23 footprint. | Select only if cost sensitivity outweighs efficiency and board space requirements; verify thermal margin with 2-layer PCB. |
Compared with TPS62231DRYR and AP3012KTR-G1, the LM3674MF-ADJ offers superior thermal performance in SOT-23 due to synchronous rectification, tighter output accuracy via 0.5-V reference, and proven reliability in high-volume mobile designs - making it optimal for cost-sensitive yet performance-critical portable power rails.
Availability
LM3674MF-ADJ is available at Aetrix Electronics and suitable for mobile phones, MP3 players, portable hard disk drives, and digital still cameras requiring stable component supply with full traceability and long-term lifecycle support.
Supply support for LM3674MF-ADJ includes scheduled delivery planning, volume procurement assistance, BOM continuity management, traceable sourcing, and lifecycle availability coordination for OEM customers, industrial embedded developers, connected-device designers, and electronics production programs.
Manufacturer
Texas Instruments is a global semiconductor company specializing in analog and embedded processing technologies, with leadership in power management ICs for portable and industrial applications.
The LM3674 product line was developed specifically for high-efficiency, low-noise, space-constrained DC-DC conversion in battery-powered consumer electronics - emphasizing integration, thermal robustness, and ease of layout.
FAQ
What is the minimum input voltage required for LM3674MF-ADJ to regulate a 1.5-V output?
The minimum input voltage for LM3674MF-ADJ to sustain 1.5 V output is calculated as VIN,MIN = VOUT + ILOAD × (RDS(ON)(P) + RL). At 300 mA load, with RDS(ON)(P) = 440 mΩ and RL = 200 mΩ, VIN,MIN ≈ 1.5 V + 0.3 A × 0.64 Ω = 1.69 V - but the device requires ≥2.7 V input per recommended operating conditions, so 2.7 V is the functional minimum for LM3674MF-ADJ.
How do I calculate the output voltage for LM3674MF-ADJ using the FB pin?
LM3674MF-ADJ regulates its output so that the FB pin voltage equals 0.5 V. To set VOUT, use two resistors: R2 from FB to GND (recommended 200 kΩ), and R1 from VOUT to FB. The formula is VOUT = 0.5 V × (1 + R1/R2). For example, to achieve 1.8 V output, select R1 = 520 kΩ (1% tolerance) with R2 = 200 kΩ - confirming VOUT = 0.5 × (1 + 520/200) = 1.8 V. This relationship holds for LM3674MF-ADJ across its full 1–3.3 V range.
Does LM3674MF-ADJ require an external Schottky diode?
No, LM3674MF-ADJ does not require an external Schottky diode because it integrates both a PFET high-side switch and an NFET synchronous rectifier. This internal synchronous rectification replaces the external diode, reducing forward voltage drop and conduction losses - improving efficiency by up to 12% compared to diode-based buck converters at 300 mA load. The SW pin connects directly to the inductor without any diode.
What is the purpose of the EN pin on LM3674MF-ADJ, and what voltage levels enable/disable it?
The EN pin on LM3674MF-ADJ controls device enable/disable state. Applying ≥1 V to EN activates regulation; applying ≤0.4 V forces shutdown mode with 0.01 µA typical quiescent current. The pin must never be left floating - tie to VIN through a pull-up resistor or to GND through a pull-down if controlled by a microcontroller GPIO. This behavior is specified across –30°C to 125°C for LM3674MF-ADJ and ensures reliable power sequencing in portable systems.
Can LM3674MF-ADJ operate in 100% duty-cycle mode, and what are the implications?
Yes, LM3674MF-ADJ supports 100% duty-cycle operation when input voltage approaches output voltage - turning the PFET fully on without switching. In this mode, regulation is maintained but output ripple increases to ~25 mV p-p due to absence of inductor filtering. The minimum input voltage for dropout is VIN,MIN = VOUT + ILOAD × (RDS(ON)(P) + RL). This feature enables LM3674MF-ADJ to extend battery runtime in low-VIN conditions where other buck converters would drop out.
LM3674MF-ADJ Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Texas Instruments
- Series:
- -
- Package/Case:
- SC-74A, SOT-753
- Packaging:
- Tape & Reel (TR)
- Product Status:
- Obsolete
- Function:
- Step-Down
- Output Configuration:
- Positive
- Topology:
- Buck
- Output Type:
- Adjustable
- Number of Outputs:
- 1
- Voltage - Input (Min):
- 2.7V
- Voltage - Input (Max):
- 5.5V
- Voltage - Output (Min/Fixed):
- 1V
- Voltage - Output (Max):
- 3.3V
- Current - Output:
- 600mA
- Frequency - Switching:
- 2MHz
- Synchronous Rectifier:
- Yes
- Operating Temperature:
- -30°C ~ 85°C (TA)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- SOT-23-5
LM3674MF-ADJ FAQ
1.How can I place an order for LM3674MF-ADJ through Aetrix?
Please submit a Request for Quotation (RFQ) for LM3674MF-ADJ on Aetrix. Our sales agent will provide a competitive quotation and guide you through the order confirmation once you accept the terms.
2.Are the price and stock information for LM3674MF-ADJ reliable?
The price and inventory of LM3674MF-ADJ are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LM3674MF-ADJ is usually 5 days.
3.What payment methods are accepted for LM3674MF-ADJ?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LM3674MF-ADJ transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LM3674MF-ADJ?
LM3674MF-ADJ orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LM3674MF-ADJ order is processed, you will receive an email with the shipment details and tracking number.
Note: Tracking information may take up to 24 hours to appear. Express delivery typically takes 3–5 business days.
5.How can I obtain technical support or documentation for LM3674MF-ADJ?
For technical support, including LM3674MF-ADJ datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LM3674MF-ADJ requirements.
6.How does Aetrix verify that LM3674MF-ADJ is sourced from the original manufacturer or authorized distributors?
All LM3674MF-ADJ products on Aetrix are procured from qualified distributors and authorized channels. Our dedicated quality assurance team conducts strict verification, including traceability checks and, if necessary, third-party testing. This ensures that LM3674MF-ADJ meets industry standards.
7.What is the process for return or replacement of LM3674MF-ADJ?
All LM3674MF-ADJ units undergo pre-shipment inspection (PSI). If there is an issue with LM3674MF-ADJ, returns or replacements are accepted under the following conditions:
1.Quantity discrepancies, incorrect items, or visible external defects (such as breakage or corrosion), acknowledged by Aetrix.
2.The issue is reported within 90 days of delivery.
3.The LM3674MF-ADJ part is unused and in its original packaging.
Return procedure for LM3674MF-ADJ:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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