Texas Instruments LP38691SDX-ADJ

Overview

LP38691SDX-ADJ from Texas Instruments is a 500-mA, adjustable-output CMOS low-dropout linear regulator in a 6-pin WSON package (3.0 mm × 3.0 mm), featuring 2% ADJ pin voltage accuracy (1.25 V ±25 mV), 250 mV typical dropout at 500 mA (V_OUT = 5 V), and stable operation with only 1-µF ceramic output capacitance. It delivers precision bias for microcontroller core rails in space-constrained portable instrumentation.

For engineers reviewing the LP38691SDX-ADJ datasheet, LP38691SDX-ADJ pinout, LP38691SDX-ADJ application, or LP38691SDX-ADJ equivalent, key selection criteria include its WSON thermal performance (R_θJA = 50.6°C/W), ultra-low ground current (55 µA typical at full load), and absence of enable functionality-distinguishing it from the LP38693-ADJ variant.

Technical Context

The LP38691SDX-ADJ uses a PMOS pass transistor to eliminate DC base drive current, enabling GND-pin current to remain below 100 µA across load, input voltage, and temperature. Its trimmed bandgap reference ensures 2% ADJ pin voltage accuracy over –40°C to +125°C, supporting industrial-grade operation without external trimming.

Stability is achieved with ultra-low-ESR ceramic capacitors (5–500 mΩ), and the device incorporates foldback current limiting (350 mA at VIN–VOUT > 5 V; 850 mA at VIN–VOUT < 4 V) and thermal shutdown activation at 160°C with 10°C hysteresis-critical for unattended battery-powered systems.

Key Specifications

Pinout & Package

LP38691SDX-ADJ is housed in a thermally enhanced 6-pin WSON package (NGG) with an exposed thermal pad (DAP) on the bottom. The DAP must be soldered to a PCB copper plane for effective heat dissipation; R_θJC(bot) = 5.4°C/W confirms direct junction-to-board conduction path.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar adjustable LDO regulator applications.

Compared with LP38693SD-ADJ, LP38691SDX-ADJ trades enable functionality for lower thermal resistance and smaller footprint; versus TLS850F0TESA1, it omits automotive safety features but offers broader input range (2.7–10 V vs. 3.5–40 V) and simpler biasing.

Availability

LP38691SDX-ADJ is available at Aetrix Electronics and suitable for portable instrumentation, battery-powered devices, and notebook computer subsystems requiring stable component supply with guaranteed long-term manufacturability.

Supply support for LP38691SDX-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 leader specializing in analog and embedded processing technologies, with decades of expertise in power management IC design and manufacturing.

The LP3869x family was developed specifically for portable, battery-powered digital systems demanding accurate output voltage, fast start-up, and ceramic-capacitor compatibility-enabling compact, low-noise power solutions.

FAQ

What is the minimum output capacitor required for stable operation of LP38691SDX-ADJ?

The LP38691SDX-ADJ requires a minimum 1-µF ceramic output capacitor for stability, with ESR between 5 mΩ and 500 mΩ. X7R or X5R dielectrics are strongly recommended to maintain capacitance across temperature and voltage; Z5U/Y5V types are discouraged due to severe capacitance loss under bias.

Does LP38691SDX-ADJ include an enable (EN) pin?

No, LP38691SDX-ADJ does not have an enable pin. It is always active when input voltage is applied. The EN pin is present only on the LP38693-ADJ variant. For applications requiring shutdown control, LP38693SD-ADJ is the functional alternative.

What is the maximum junction temperature and thermal protection behavior of LP38691SDX-ADJ?

LP38691SDX-ADJ activates thermal shutdown at approximately 160°C junction temperature and resumes operation after cooling to ~150°C (10°C hysteresis). This cycling protects against permanent damage during sustained overload but is not a substitute for proper heatsinking via the exposed thermal pad.

How is the output voltage set on LP38691SDX-ADJ?

Output voltage is set using an external resistor divider connected to the ADJ pin: V_OUT = 1.25 V × (1 + R1/R2). R2 should be ≤12 kΩ to ensure ≥100 µA minimum load current; R1 and R2 combined should not exceed 100 kΩ to avoid noise susceptibility at the ADJ node.

What is the ground (GND) pin current specification for LP38691SDX-ADJ at full load?

LP38691SDX-ADJ exhibits 55 µA typical GND-pin current at full 500 mA load, with a maximum of 100 µA across all operating conditions. This ultra-low value results from the PMOS pass transistor architecture and enables high-efficiency operation in battery-critical applications.