Texas Instruments LM3674MFX-1.5

Overview

LM3674MFX-1.5 from Texas Instruments is a fixed-output 1.5 V, 2-MHz synchronous step-down DC-DC converter optimized for single Li-Ion battery-powered systems. It delivers up to 600 mA load current across 2.7–5.5 V input range, features internal soft-start, 0.01 µA shutdown current, and operates in a 5-pin SOT-23 package. It powers core logic rails in compact portable electronics where space and efficiency are critical.

For engineers reviewing the LM3674MFX-1.5 datasheet, LM3674MFX-1.5 pinout, LM3674MFX-1.5 application, or LM3674MFX-1.5 equivalent, key selection criteria include its fixed 1.5 V output, 2 MHz switching frequency enabling ultra-small external components (2.2 µH inductor, 4.7 µF CIN, 10 µF COUT), synchronous rectification for >90% efficiency at mid-load, and thermal/overcurrent protection for robust operation in thermally constrained handheld designs.

Technical Context

The LM3674MFX-1.5 uses voltage-mode PWM control with input voltage feed-forward to maintain tight line regulation (0.083%/V) and load regulation (0.0010%/mA). Its internal 0.5 V reference and fixed resistor divider enable precise 1.5 V output without external feedback components.

It integrates a 380 mΩ PFET high-side switch and 250 mΩ NFET synchronous rectifier, enabling high efficiency down to light loads. The device transitions seamlessly between PWM mode (2 MHz typical) and shutdown mode (0.01 µA IQ), with undervoltage lockout preventing operation below 2.7 V input.

Key Specifications

Pinout & Package

LM3674MFX-1.5 is housed in a 5-pin SOT-23 (DBV) package measuring 2.90 mm × 1.60 mm, optimized for high-density portable PCBs with minimal thermal pad area.

Key Features

Applications

Equivalent & Alternatives

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

Compared with TPS62231DRYR and AP63202-W5-7, the LM3674MFX-1.5 offers the widest input range (2.7 V min) for reliable Li-Ion operation across full discharge, built-in soft-start eliminating external components, and lowest shutdown current-making it optimal for long-life, battery-critical portable systems.

Availability

LM3674MFX-1.5 is available at Aetrix Electronics and suitable for mobile phones, wearable sensors, digital still cameras, and portable medical devices requiring stable component supply, consistent parametric performance, and long-term production continuity.

Supply support for LM3674MFX-1.5 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 leader specializing in analog and embedded processing technologies, with decades of expertise in power management ICs for portable and industrial applications.

The LM3674 product line was designed specifically for space-constrained, battery-powered portable electronics requiring high-efficiency, low-quiescent-current DC-DC conversion with minimal external components.

FAQ

What is the minimum input voltage required for LM3674MFX-1.5 to regulate 1.5 V output?

The LM3674MFX-1.5 requires a minimum input voltage of 2.7 V to initiate and sustain regulation. Below this threshold, undervoltage lockout disables switching to prevent unstable operation. This 2.7 V minimum aligns with the end-of-discharge voltage of a single Li-Ion cell, ensuring full utilization of battery capacity. The LM3674MFX-1.5 will not operate at 2.6 V or lower, even with light load.

Does LM3674MFX-1.5 require external feedback resistors to set its 1.5 V output?

No, the LM3674MFX-1.5 does not require external feedback resistors. It integrates a precision 0.5 V internal reference and a factory-trimmed resistor divider that fixes the output at 1.5 V. Pin 4 (FB) is internally connected to this divider, so no external components are needed-unlike the adjustable LM3674-ADJ variant. This simplifies design, reduces BOM count, and improves output accuracy.

What inductor value is recommended for LM3674MFX-1.5, and why?

A 2.2 µH shielded inductor with ≥1200 mA saturation current is recommended for the LM3674MFX-1.5. This value balances ripple current (≈300 mA peak-to-peak at 300 mA load), efficiency (>92% at mid-load), and physical size-enabling use of compact 3.3 mm × 3.3 mm footprints. The 2.2 µH value is validated in TI's SNVS405G datasheet Figure 9 and supports stable 2 MHz operation without subharmonic oscillation.

How does LM3674MFX-1.5 handle short-circuit conditions on its output?

The LM3674MFX-1.5 responds to output short-circuit with cycle-by-cycle current limiting (1020 mA typical peak) followed by thermal shutdown if sustained. During short-circuit, the device enters timed current-limit mode: the NFET remains on longer to allow inductor current decay, preventing runaway. If junction temperature exceeds 125°C, thermal shutdown activates and the device halts switching until cooled. This dual-layer protection preserves reliability in fault-prone portable environments.

Can LM3674MFX-1.5 be used with ceramic capacitors only, and what are the minimum values?

Yes, the LM3674MFX-1.5 is designed for all-ceramic operation. Minimum recommended values are 4.7 µF (X5R/X7R, 6.3 V) for CIN and 10 µF (X5R/X7R, 6.3 V) for COUT-both in 0805 case size. These values ensure stability, low ESR for ripple suppression, and adequate capacitance under DC bias. Using Y5V dielectrics or undersized capacitors may cause instability or excessive output ripple due to bias-induced capacitance loss.