Texas Instruments LM3674MFX-1.2/NOPB

Overview

LM3674MFX-1.2/NOPB from Texas Instruments is a fixed-output 1.2 V, 600-mA synchronous step-down DC-DC converter optimized for single Li-Ion battery-powered portable electronics. It operates from 2.7 V to 5.5 V input, delivers up to 600 mA load current, features 2 MHz fixed-frequency PWM operation, internal soft-start, and 0.01 µA shutdown current - enabling compact, high-efficiency power delivery in space-constrained mobile applications.

For engineers reviewing the LM3674MFX-1.2/NOPB datasheet, LM3674MFX-1.2/NOPB pinout, LM3674MFX-1.2/NOPB application, or LM3674MFX-1.2/NOPB equivalent, key selection criteria include its SOT-23-5 package footprint, 1.2 V fixed output with ±4% feedback voltage tolerance, 2 MHz switching frequency enabling use of tiny 2.2 µH inductors and 10 µF ceramic output capacitors, and integrated PFET/NFET synchronous rectification for high efficiency at low output voltages.

Technical Context

The LM3674MFX-1.2/NOPB employs voltage-mode PWM control with input voltage feed-forward to achieve tight line and load regulation. Its internal 0.5 V reference feeds an error amplifier that compares FB voltage against VREF to modulate PFET on-time at a fixed 2 MHz clock rate.

During each cycle, the PFET switch conducts to ramp inductor current upward; then the NFET synchronous rectifier turns on to ramp current downward, minimizing conduction loss. Current limiting (1020 mA typical) and thermal shutdown protect the device under overload or overtemperature conditions.

Key Specifications

Pinout & Package

SOT-23-5 (DBV) package: 2.90 mm × 1.60 mm body, 0.95 mm height, gull-wing leads, RoHS-compliant / NOPB finish.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar step-down converter applications.

Compared with TPS62231DRVR and AP63201WS-7, the LM3674MFX-1.2/NOPB offers the lowest shutdown current (0.01 µA) and integrated soft-start in the same SOT-23-5 footprint, making it optimal for battery-critical portable designs where minimal quiescent loss and controlled start-up are mandatory.

Availability

LM3674MFX-1.2/NOPB is available at Aetrix Electronics and suitable for mobile phones, WLAN modules, portable digital cameras, and MP3 players requiring stable component supply with guaranteed long-term sourcing and consistent parametric performance.

Supply support for LM3674MFX-1.2/NOPB 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, designing and manufacturing analog, embedded processing, and logic ICs for industrial, automotive, and consumer markets.

The LM3674 product line was developed specifically for ultra-compact, high-efficiency power conversion in battery-powered portable electronics - emphasizing minimal external component count, low quiescent current, and robust protection features for Li-Ion systems.

FAQ

What is the recommended input and output capacitor configuration for LM3674MFX-1.2/NOPB?

The LM3674MFX-1.2/NOPB requires a 4.7 µF X5R/X7R ceramic capacitor (6.3 V rating) placed adjacent to the VIN pin and a 10 µF X5R/X7R ceramic capacitor (6.3 V rating) connected directly between VOUT and GND. These values ensure stable operation, low ripple (<25 mV peak-to-peak), and adequate transient response. The LM3674MFX-1.2/NOPB datasheet specifies minimum values of 2.2 µF (C_IN) and 5.75 µF (C_OUT) under worst-case DC bias and temperature conditions.

Does LM3674MFX-1.2/NOPB require external feedback resistors?

No, the LM3674MFX-1.2/NOPB is a fixed-output variant with internal resistor divider configured for 1.2 V. The FB pin connects directly to the VOUT net; no external R1/R2 network is needed. This simplifies layout and eliminates resistor tolerance errors. In contrast, the LM3674-ADJ version requires external resistors to set the output voltage, but the LM3674MFX-1.2/NOPB uses factory-trimmed internal resistors for precise 1.2 V regulation.

What thermal performance can be expected from LM3674MFX-1.2/NOPB in a standard 2-layer PCB?

On a standard 2-layer PCB, the LM3674MFX-1.2/NOPB has a junction-to-ambient thermal resistance (R_θJA) of 250°C/W. At 600 mA load and 3.6 V input, power dissipation is ~360 mW, resulting in ~90°C junction rise above ambient. Derating is required above 60°C ambient to maintain TJ ≤125°C. For higher reliability, use a 4-layer board (R_θJA = 130°C/W) or add thermal vias under the exposed pad (though SOT-23-5 has no thermal pad).

How does the soft-start function operate in LM3674MFX-1.2/NOPB?

The LM3674MFX-1.2/NOPB implements internal soft-start by progressively increasing the switch current limit in four steps: 70 mA → 140 mA → 280 mA → 1020 mA (typical). This occurs only when EN transitions from low to high after VIN reaches ≥2.7 V. Start-up time depends on output capacitance and load - e.g., 240 µs with 10 µF C_OUT and 10 mA load, or 350 µs at 300 mA. The LM3674MFX-1.2/NOPB does not require external soft-start components.

Is LM3674MFX-1.2/NOPB pin-compatible with other members of the LM3674 family?

Yes, all LM3674 variants - including LM3674MFX-1.2/NOPB, LM3674MFX-1.5/NOPB, LM3674MFX-1.8/NOPB, LM3674MFX-2.5/NOPB, LM3674MFX-2.8/NOPB, LM3674MFX-3.3/NOPB, and LM3674-ADJ - share identical SOT-23-5 (DBV) packaging and pinout. This enables drop-in replacement across output voltages without PCB redesign, provided input voltage and load requirements remain within spec.