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Texas Instruments LM3674MFX-ADJ
- Part No.:
- LM3674MFX-ADJ
- Manufacturer:
- Texas Instruments
- Package:
- SC-74A, SOT-753
- Datasheet:
-
LM3674MFX-ADJ.pdf
- Description:
- IC REG BUCK ADJ 600MA SOT23-5
- Quantity:
- Payment:
- Shipping:
Inventory:1,290
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Product details
Overview
LM3674MFX-ADJ from Texas Instruments is a 2-MHz, 600-mA synchronous step-down DC-DC converter in SOT-23-5 package, designed for single Li-Ion battery-powered systems (2.7 V to 5.5 V input), delivering adjustable output voltages from 1 V to 3.3 V via external resistor divider, with 0.5-V internal reference and 0.01-µA shutdown current. It enables compact power solutions in space-constrained portable electronics.
For engineers reviewing the LM3674MFX-ADJ datasheet, LM3674MFX-ADJ pinout, LM3674MFX-ADJ application, or LM3674MFX-ADJ equivalent, key selection criteria include its 2-MHz fixed-frequency PWM operation, internal synchronous rectification, soft-start functionality, thermal/overcurrent protection, and compatibility with only three external components (2.2-µH inductor, 4.7-µF CIN, 10-µF COUT).
Technical Context
The LM3674MFX-ADJ employs voltage-mode PWM control with input voltage feed-forward to achieve tight line and load regulation. Its internal 0.5-V reference sets output voltage via external R1/R2 feedback network, enabling precise adjustment across 1 V–3.3 V range.
It integrates a PFET high-side switch (RDSON(P) = 380–500 mΩ) and NFET synchronous rectifier (RDSON(N) = 250–400 mΩ), operating at 2 MHz (1.6–2.6 MHz over temperature) to minimize external component size. Protection features include cycle-by-cycle current limiting (1020 mA typical), thermal shutdown, undervoltage lockout, and soft-start with stepped current limit (70/140/280/1020 mA).
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Input Voltage Range | 2.7 V to 5.5 V - supports full operation from single Li-Ion cell (3.0–4.2 V nominal) with margin for discharge and charging transients. |
| Output Current | 600 mA max - delivers full rated load across entire input range and ambient temperature (–30°C to +85°C). |
| Switching Frequency | 2 MHz typical - enables use of small 2.2-µH shielded inductors and low-ESR ceramic capacitors (CIN = 4.7 µF, COUT = 10 µF). |
| Feedback Reference | 0.5 V - sets output via external resistor divider; allows precise 1 V–3.3 V adjustment with minimal divider current (2.5 µA at R2 = 200 kΩ). |
| Shutdown Current | 0.01 µA typical - minimizes battery drain in standby mode; EN pin logic-low disables switching and reduces quiescent draw. |
| Protection Features | Thermal shutdown, current overload limit (1020 mA typ), undervoltage lockout - ensures robust operation under fault conditions without external circuitry. |
| Efficiency | Up to 94% at 300 mA (VOUT = 1.5 V, VIN = 3.6 V) - achieved via synchronous rectification eliminating Schottky diode losses. |
Pinout & Package
SOT-23-5 (DBV) package, 2.90 mm × 1.60 mm body size, with exposed pad for thermal enhancement (not electrically connected). Pin 1 is VIN; pin 2 is GND; pin 3 is EN; pin 4 is FB; pin 5 is SW.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| VIN (Pin 1) | Power input | Connects to input filter capacitor (4.7 µF ceramic); must be ≥2.7 V for enable; supplies PFET switch and internal bias rails. |
| GND (Pin 2) | Ground reference | Primary return path for input/output currents and internal control circuits; requires low-impedance PCB connection to minimize noise and thermal rise. |
| EN (Pin 3) | Enable control | Digital input: >1 V enables operation; <0.4 V forces shutdown (0.01 µA IQ); must not float - tie to VIN or microcontroller GPIO. |
| FB (Pin 4) | Feedback sense | Analog input monitoring output voltage via resistor divider; internal 0.5-V reference sets VOUT = 0.5 × (1 + R1/R2); disables internal fixed-divider in ADJ version. |
| SW (Pin 5) | Switch node | Connection to internal PFET drain and NFET source; carries high di/dt switching current - requires short, wide trace to inductor and minimized loop area. |
Key Features
| Feature | Design Value |
|---|---|
| Internal Synchronous Rectification | Eliminates external Schottky diode; reduces conduction loss by replacing ~0.3-V forward drop with 250–400 mΩ NFET RDS(on), improving efficiency especially at low VOUT. |
| 2-MHz Fixed-Frequency PWM | Enables use of tiny 2.2-µH inductors and 0805-case ceramics; avoids audible noise and simplifies EMI filtering compared to variable-frequency architectures. |
| Programmable Output Voltage | Supports 1 V–3.3 V via external R1/R2; R2 = 200 kΩ recommended for 2.5-µA divider current - balances accuracy, noise immunity, and power loss. |
| Integrated Soft-Start | Staged current limit (70→140→280→1020 mA) prevents inrush into large output capacitors; typical start-up time is 240–350 µs with 10-µF COUT and 10–300 mA load. |
| Low Shutdown Current | 0.01 µA typical draw in EN = low state - extends battery life in sleep modes of mobile devices without requiring external load switches. |
Applications
| Mobile Phone Power Rail | PDA Core Voltage Supply |
|---|---|
Use Scenario: Generating 1.2 V core voltage for ARM-based application processor in slim smartphone design with single-cell Li-Ion battery. IC Role / Device Role / Timing Role: Primary buck regulator providing regulated, low-noise DC supply; operates continuously in PWM mode during active use and enters shutdown during deep sleep. Use Value: 2-MHz switching allows 2.2-µH inductor and 10-µF ceramic output cap - reducing solution footprint by >40% vs lower-frequency alternatives while maintaining 92% efficiency at 400 mA. | Use Scenario: Delivering adjustable 1.8 V I/O voltage for touchscreen controller and memory interface in handheld PDA with tight thermal constraints. IC Role / Device Role / Timing Role: Adjustable-output DC-DC converter enabling flexible rail configuration; FB pin configured with precision resistors for ±1% output accuracy. Use Value: Internal 0.5-V reference and low FB bias current (50 nA typ) ensure stable regulation despite PCB leakage and temperature drift, supporting long-term reliability in consumer handhelds. |
| MP3 Player Audio Codec Supply | WLAN Module RF Front-End Bias |
Use Scenario: Providing clean 3.3 V analog supply to stereo audio DAC/ADC in battery-powered MP3 player with dynamic load ranging 10–200 mA. IC Role / Device Role / Timing Role: High-efficiency step-down converter with low output ripple (<25 mVpp) due to synchronous rectification and optimized LC filter. Use Value: 94% peak efficiency at 150 mA and <10 µVrms output noise enable high-fidelity audio playback without audible switching artifacts or supply-induced distortion. | Use Scenario: Generating 1.5 V bias for WLAN transceiver RF power amplifier in compact IoT module powered by 3.6-V Li-Ion cell. IC Role / Device Role / Timing Role: Compact, thermally robust buck regulator handling pulsed 500-mA peak loads during TX bursts while maintaining regulation during RX low-power states. Use Value: Thermal shutdown and cycle-by-cycle current limiting protect against antenna mismatch or PA failure; 0.01-µA shutdown current preserves battery during extended idle periods. |
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 | 3-MHz switching frequency, 300-mA output, 0.6-V reference, smaller 1.5-mm × 1.5-mm DSBGA package | Better suited for ultra-compact layouts but lower current capability; lacks thermal shutdown flag output | Select when board area is critical and load ≤300 mA; verify thermal performance under 5.5-V input/1.5-V output worst case. |
| AP3012KTR-G1 | 1.5-MHz frequency, 600-mA output, 0.5-V reference, SOT-23-5 package, no integrated soft-start | Requires external soft-start circuit for inrush control; slightly lower efficiency at light loads due to non-synchronous rectification | Choose for cost-sensitive designs where soft-start timing is non-critical and 2–3% efficiency penalty at 10 mA is acceptable. |
Compared with TPS62231DRYR and AP3012KTR-G1, the LM3674MFX-ADJ provides superior thermal robustness (integrated thermal shutdown), higher efficiency across 10–600 mA loads (due to synchronous rectification), and simpler implementation (integrated soft-start, no external compensation required), making it optimal for reliable, high-density portable power rails.
Availability
LM3674MFX-ADJ is available at Aetrix Electronics and suitable for mobile phones, PDAs, MP3 players, portable instruments, and WLAN modules requiring stable component supply, long-lifecycle support, and consistent parametric performance across production batches.
Supply support for LM3674MFX-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 headquartered in Dallas, Texas, specializing in analog, embedded processing, and power management ICs for industrial, automotive, and consumer markets.
The LM3674 product line was engineered specifically for space-constrained, battery-powered portable electronics, emphasizing ultra-small solution size, high efficiency at light-to-moderate loads, and robust protection in unpredictable operating environments.
FAQ
What is the minimum input voltage required for LM3674MFX-ADJ to regulate a 1.5-V output?
The LM3674MFX-ADJ requires VIN ≥ (ILOAD × (RDSON(P) + RINDUCTOR)) + VOUT to maintain regulation. At 300 mA load, RDSON(P) ≈ 440 mΩ, and with a typical 200-mΩ inductor, minimum VIN is ~1.5 V + (0.3 A × 0.64 Ω) = 1.69 V - but per datasheet, the absolute minimum recommended VIN is 2.7 V to ensure stable startup, soft-start activation, and proper UVLO behavior. Below 2.7 V, the device may not enable or could exhibit erratic regulation.
How do I calculate the resistor values for setting a 2.1-V output on LM3674MFX-ADJ?
Use the formula VOUT = VFB × (1 + R1/R2), where VFB = 0.5 V. For VOUT = 2.1 V, (1 + R1/R2) = 4.2 → R1/R2 = 3.2. With R2 = 200 kΩ (recommended for noise immunity and low divider current), R1 = 3.2 × 200 kΩ = 640 kΩ. Standard 1% E96 value is 634 kΩ. Verify resulting VOUT tolerance accounts for R1/R2 ratio error, VFB drift (±4%), and resistor tempcos.
Does LM3674MFX-ADJ require external compensation components?
No, the LM3674MFX-ADJ uses internal frequency compensation and is optimized for stability with the standard 2.2-µH inductor and 10-µF ceramic output capacitor. The voltage-mode architecture with feed-forward eliminates need for external RC networks or type-II/type-III compensators - simplifying layout and reducing BOM count.
Can LM3674MFX-ADJ operate in 100% duty cycle for low-dropout operation?
Yes, the LM3674MFX-ADJ supports 100% duty cycle (PFET fully enhanced, no switching) when VIN is near VOUT, enabling LDO-like operation. In this mode, output ripple increases to ~25 mVpp due to absence of inductor filtering. Minimum VIN for dropout is calculated as VIN,MIN = ILOAD × (RDSON(P) + RINDUCTOR) + VOUT - e.g., 300 mA into 1.5 V yields ~1.69 V theoretical minimum, though 2.7 V is required for guaranteed functional operation.
What is the thermal resistance (RθJA) of LM3674MFX-ADJ in standard PCB layout?
The LM3674MFX-ADJ in SOT-23-5 (DBV) package has RθJA = 250°C/W on a 2-layer board and 130°C/W on a 4-layer board per TI SNVS405G. These values assume standard JEDEC test conditions (1-inch² copper pad, 1-oz copper). Actual board-level RθJA depends on copper area, vias to inner layers, and airflow - derate power dissipation accordingly using TA-MAX = TJ-MAX – (RθJA × PD-MAX), where TJ-MAX = 125°C.
LM3674MFX-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
LM3674MFX-ADJ FAQ
1.How can I place an order for LM3674MFX-ADJ through Aetrix?
Please submit a Request for Quotation (RFQ) for LM3674MFX-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 LM3674MFX-ADJ reliable?
The price and inventory of LM3674MFX-ADJ are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LM3674MFX-ADJ is usually 5 days.
3.What payment methods are accepted for LM3674MFX-ADJ?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LM3674MFX-ADJ transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LM3674MFX-ADJ?
LM3674MFX-ADJ orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LM3674MFX-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 LM3674MFX-ADJ?
For technical support, including LM3674MFX-ADJ datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LM3674MFX-ADJ requirements.
6.How does Aetrix verify that LM3674MFX-ADJ is sourced from the original manufacturer or authorized distributors?
All LM3674MFX-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 LM3674MFX-ADJ meets industry standards.
7.What is the process for return or replacement of LM3674MFX-ADJ?
All LM3674MFX-ADJ units undergo pre-shipment inspection (PSI). If there is an issue with LM3674MFX-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 LM3674MFX-ADJ part is unused and in its original packaging.
Return procedure for LM3674MFX-ADJ:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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