Texas Instruments LM3691TL-1.5/NOPB

Overview

LM3691TL-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 devices requiring stable low-noise 1.5 V supply under dynamic load.

For engineers reviewing the LM3691TL-1.5/NOPB datasheet, LM3691TL-1.5/NOPB pinout, LM3691TL-1.5/NOPB application, or LM3691TL-1.5/NOPB equivalent, key selection criteria include its 1.5 V fixed output, DSBGA-6 package footprint (<15 mm² solution size), 64 µA typical quiescent current in ECO mode, and integrated PFET/NFET synchronous rectification enabling >85% efficiency at 100 mA with VIN = 3.6 V.

Technical Context

The LM3691TL-1.5/NOPB employs voltage-mode control with input-voltage feed-forward to achieve tight line and load regulation across its 2.3 V–5.5 V input range. Its internal architecture integrates a 160 mΩ PFET high-side switch and 115 mΩ NFET synchronous rectifier, enabling continuous 1-A output capability while maintaining <30 mV peak-to-peak output ripple in ECO mode.

Operation spans three distinct functional states: shutdown (0.03 µA IQ), ECO mode (64 µA IQ, gated PWM, 30 mV higher reference), and forced PWM mode (490 µA IQ, constant 4-MHz switching). Mode selection is controlled via the MODE pin, while EN enables/disables the converter with undervoltage lockout (UVLO) active below 2.1 V.

Key Specifications

Pinout & Package

The LM3691TL-1.5/NOPB is housed in a 6-pin DSBGA package measuring 1.59 mm × 1.295 mm with 0.5-mm pitch, optimized for ultra-compact portable PCB layouts.

Key Features

Applications

Equivalent & Alternatives

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

Compared with TPS62231DRYR and RT8059GJ6, the LM3691TL-1.5/NOPB delivers superior transient response (<50 µs recovery) and wider input range (2.3 V min), making it optimal for portable devices requiring robust operation across full battery discharge curves and fast load changes.

Availability

LM3691TL-1.5/NOPB is available at Aetrix Electronics and suitable for mobile phones, MP3 players, hand-held radios, and portable hard disk drives requiring stable component supply, long-term lifecycle support, and RoHS-compliant packaging.

Supply support for LM3691TL-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 IC design for portable and industrial applications.

The LM3691TL-1.5/NOPB belongs to TI's high-efficiency miniature buck converter product line, engineered specifically for space-constrained battery-powered devices demanding precise low-voltage rails, ultra-low quiescent current, and seamless mode transitions.

FAQ

What is the output voltage tolerance of the LM3691TL-1.5/NOPB over temperature and line?

The LM3691TL-1.5/NOPB guarantees ±1% DC output voltage accuracy across the full operating ambient temperature range (–30°C to +85°C) and input voltage range (2.3 V to 5.5 V). This specification is confirmed in the Electrical Characteristics table of the SNVS506J datasheet under the VFB parameter, with no external components required to achieve this precision since the 1.5 V reference is factory-trimmed and internal to the LM3691TL-1.5/NOPB.

Does the LM3691TL-1.5/NOPB require external feedback resistors to set its output voltage?

No, the LM3691TL-1.5/NOPB does not require external feedback resistors. As a fixed-output variant, it integrates an internal 1.5 V reference connected directly to the FB pin (C1), eliminating the need for a resistor divider. This simplifies design, reduces component count, and ensures consistent 1.5 V regulation without calibration - a key feature distinguishing the LM3691TL-1.5/NOPB from adjustable versions like the LM3691.

How does the MODE pin affect the efficiency profile of the LM3691TL-1.5/NOPB?

When the MODE pin is pulled low, the LM3691TL-1.5/NOPB enters auto ECO/PWM mode, switching to 64 µA-quiescent ECO mode below ~50 mA load and to 490 µA PWM mode above that threshold - maximizing average efficiency across variable loads. With MODE high, it remains in forced PWM mode regardless of load, sacrificing light-load efficiency for tighter output regulation and faster transient response. This behavior is documented in Section 8.4.1 of the LM3691TL-1.5/NOPB datasheet.

What is the minimum input voltage required for the LM3691TL-1.5/NOPB to maintain regulation at full 1-A load?

The LM3691TL-1.5/NOPB maintains regulation at 1-A load down to 2.3 V input, as specified in the Recommended Operating Conditions table (Section 7.3). However, Table 1 (Maximum Overtemperature Load Recommendations) indicates that at VIN = 2.3 V–2.5 V, the maximum sustainable load is reduced to 650 mA to prevent thermal overload. Thus, for guaranteed 1-A operation, VIN must be ≥2.5 V - a critical constraint verified in the LM3691TL-1.5/NOPB thermal derating guidelines.

Can the LM3691TL-1.5/NOPB be used with ceramic output capacitors smaller than 4.7 µF?

Yes, the LM3691TL-1.5/NOPB can operate with output capacitance as low as 2.2 µF, as stated in Section 9.2.2.3 of the datasheet ("Minimum output capacitance to specify good performance is 2.2 µF"). However, using 4.7 µF is recommended to ensure <30 mVpp ripple in ECO mode and adequate transient response margin. Capacitor selection must prioritize X7R/X5R dielectrics with sufficient DC bias rating - Y5V types are explicitly prohibited for the LM3691TL-1.5/NOPB.