Texas Instruments LM3691TLX-1.5/NOPB

Overview

LM3691TLX-1.5/NOPB from Texas Instruments is a high-accuracy, miniature 1-A synchronous step-down DC-DC converter optimized for ultra-low-voltage portable systems powered by single-cell Li-Ion (2.3 V–5.5 V input) and delivering a fixed 1.5 V output with ±1% DC precision, 4-MHz switching frequency, and automatic ECO/PWM mode switching. It serves as the primary power rail regulator in space-constrained mobile applications requiring stable low-noise voltage under dynamic load.

For engineers reviewing the LM3691TLX-1.5/NOPB datasheet, LM3691TLX-1.5/NOPB pinout, LM3691TLX-1.5/NOPB application, or LM3691TLX-1.5/NOPB equivalent, key selection criteria include its 1.5 V fixed output, DSBGA-6 package footprint (<15 mm² solution size), 64-μA ECO-mode quiescent current, thermal/overcurrent protection, and compatibility with only three external components (1-μH inductor, two 4.7-μF ceramic caps).

Technical Context

The LM3691TLX-1.5/NOPB implements voltage-mode control with input-voltage feed-forward to maintain tight line regulation across its 2.3 V–5.5 V input range. Its synchronous rectification uses an internal PFET/NFET pair with typical R_DS(ON) of 250 mΩ (P) and 180 mΩ (N), enabling >90% peak efficiency at 100–500 mA loads with V_IN = 3.6 V and V_OUT = 1.5 V.

It supports dual operational modes: forced PWM (MODE ≥ 1.2 V) for constant-frequency operation and ECO mode (MODE ≤ 0.4 V) that dynamically gates switching to reduce IQ to 64 μA at light loads (<50 mA), increasing output ripple to 30 mV_PP while extending battery runtime. Soft-start limits inrush current with a 30 mV/μs ramp rate at V_OUT = 1.5 V.

Key Specifications

Pinout & Package

LM3691TLX-1.5/NOPB is housed in a 6-pin DSBGA (YZR) package measuring 1.59 mm × 1.295 mm with bottom-side ball layout. The package supports fine-pitch assembly and requires controlled thermal relief on GND connections for optimal power dissipation.

Key Features

Applications

Equivalent & Alternatives

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

Compared with LM3691TLX-1.5/NOPB, TPS62231DRYR offers lower quiescent current but forfeits manual MODE pin control, while RT8059GJ6 saves board area yet omits thermal shutdown-making LM3691TLX-1.5/NOPB the balanced choice for portable systems needing both efficiency control and robust protection.

Availability

LM3691TLX-1.5/NOPB is available at Aetrix Electronics and suitable for mobile phones, wearable sensor hubs, Bluetooth audio SoCs, portable medical monitors, and handheld radios requiring stable component supply with full lifecycle support.

Supply support for LM3691TLX-1.5/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 leader specializing in analog and embedded processing technologies, with decades of expertise in power management ICs for portable and industrial applications.

The LM3691 product line delivers miniature, high-efficiency step-down converters for battery-powered portable electronics, emphasizing minimal external components, adaptive light-load efficiency, and robust protection in ultra-small packages.

FAQ

What is the output voltage tolerance of the LM3691TLX-1.5/NOPB?

The LM3691TLX-1.5/NOPB provides a fixed 1.5 V output with ±1% DC accuracy over temperature (−30°C to +85°C), input voltage (2.3 V to 5.5 V), and load (0–1000 mA). This tight tolerance is achieved via factory-trimmed internal feedback and ensures reliable operation of sensitive digital cores without external calibration. The LM3691TLX-1.5/NOPB maintains this specification without requiring external resistors or compensation networks.

Does the LM3691TLX-1.5/NOPB require external feedback resistors?

No, the LM3691TLX-1.5/NOPB is a fixed-output variant with the feedback network integrated internally to set 1.5 V. Pin C1 (FB) is not connected in this version and must remain unpopulated per the datasheet. Using external resistors would disrupt the factory-trimmed regulation and void the ±1% output accuracy guarantee. The LM3691TLX-1.5/NOPB is designed for plug-and-play deployment with only three external passive components.

How does the MODE pin affect efficiency and ripple in the LM3691TLX-1.5/NOPB?

When the MODE pin is pulled low (<0.4 V), the LM3691TLX-1.5/NOPB enters ECO mode, reducing quiescent current to 64 μA at light loads (<50 mA) but increasing output ripple to 30 mV_PP. When pulled high (>1.2 V), it forces continuous PWM mode with higher IQ (490 μA) but lower ripple (<10 mV_PP). The LM3691TLX-1.5/NOPB automatically switches between modes based on load if MODE is left floating (not recommended), but explicit control enables predictable trade-offs.

What protection features are built into the LM3691TLX-1.5/NOPB?

The LM3691TLX-1.5/NOPB integrates thermal shutdown (engages at ~150°C, resumes at ~130°C), cycle-by-cycle current limiting (1500 mA typical), undervoltage lockout (UVLO falling threshold at 2.1 V), and soft-start (30 mV/μs ramp). These functions operate autonomously without external components. During overload, the LM3691TLX-1.5/NOPB disables synchronous rectification and reduces switching frequency to prevent thermal runaway-ensuring safe operation in portable enclosures.

Can the LM3691TLX-1.5/NOPB operate from a fully discharged Li-Ion cell?

Yes, the LM3691TLX-1.5/NOPB supports input voltages as low as 2.3 V, enabling operation down to the end-of-discharge voltage of a single Li-Ion cell (typically ~2.7 V nominal, ~2.5 V under load). Its UVLO threshold is 2.1 V (falling), providing margin before cutoff. At V_IN = 2.3 V and V_OUT = 1.5 V, the LM3691TLX-1.5/NOPB delivers up to 650 mA (per overtemperature derating table), making it suitable for deep-discharge portable use cases.