Texas Instruments LP38690SDX-1.8

Overview

LP38690SDX-1.8 from Texas Instruments is a 1-A, 1.8-V fixed-output low-dropout CMOS linear regulator in WSON-6 package, featuring 2.5% output accuracy at 25°C, 950 mV dropout at 1 A (V_OUT = 1.8 V), and stable operation with only 1-µF ceramic output capacitance. It delivers precision voltage regulation for battery-powered microcontrollers and portable instrumentation where low quiescent current (55 µA typical) and thermal robustness are critical.

For engineers reviewing the LP38690SDX-1.8 datasheet, LP38690SDX-1.8 pinout, LP38690SDX-1.8 application, or LP38690SDX-1.8 equivalent, key selection considerations include its WSON-6 thermal performance (R_θJB = 24.9°C/W), absence of enable pin (distinguishing it from LP38692), SNS pin for remote sensing, and guaranteed –40°C to 125°C operation with foldback current limiting.

Technical Context

The LP38690SDX-1.8 uses a PMOS pass transistor architecture enabling ultra-low ground pin current (<100 µA across load/temperature/voltage), eliminating base drive losses. Its trimmed bandgap reference and internal feedback network ensure 2.5% output tolerance over full temperature range without external resistors.

Thermal shutdown activates at 160°C junction temperature with 10°C hysteresis, and foldback current limiting responds dynamically to VIN–VOUT differential: limits to 450 mA when ΔV > 5 V, but permits up to 1500 mA when ΔV < 4 V-enabling safe startup into large capacitive loads while protecting against sustained overload.

Key Specifications

Pinout & Package

LP38690SDX-1.8 is housed in a 3.00 mm × 3.00 mm, 6-bump WSON package with exposed thermal pad (DAP) on bottom. The DAP must be soldered to a PCB copper plane for effective heat dissipation (R_θJB = 24.9°C/W).

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar low-dropout linear regulator applications.

Compared with TLS850F0TESK and TPS7A2018PDQNR, LP38690SDX-1.8 uniquely balances 1-A capability, WSON thermal performance, remote sensing, and industrial temperature guarantee-making it the only option among the three qualified for sustained 1-A loads in compact, high-ambient environments without external thermal management.

Availability

LP38690SDX-1.8 is available at Aetrix Electronics and suitable for hard disk drives, notebook computers, battery-powered devices, portable instrumentation, and industrial embedded systems requiring stable component supply with guaranteed long-term manufacturability.

Supply support for LP38690SDX-1.8 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 ICs, embedded processors, and system-on-chip solutions for industrial, automotive, and personal electronics markets.

The LP38690 series belongs to TI's precision low-dropout linear regulator product line, engineered specifically for portable and battery-operated systems demanding high accuracy, low noise, and ceramic-capacitor stability without enable control overhead.

FAQ

What is the function of the SNS pin on the LP38690SDX-1.8?

The SNS (sense) pin on the LP38690SDX-1.8 is an input that connects directly to the load-side output node to enable remote voltage sensing. It compensates for voltage drop across PCB traces between the regulator and load, ensuring the regulated 1.8 V is maintained precisely at the point-of-load. For LP38690SDX-1.8, the SNS pin must be tied to the same net as OUT at the load connector-not at the regulator's OUT pin-to achieve ±2.5% accuracy under dynamic load conditions.

Does the LP38690SDX-1.8 have an enable (EN) pin?

No, the LP38690SDX-1.8 does not include an enable pin. It is a permanently enabled device-output regulation begins whenever input voltage exceeds the minimum operating threshold (~2.7 V). This distinguishes it from the LP38692 family, which features an EN pin for external on/off control. If enable functionality is required, LP38692SDX-1.8 (SOT-223 or WSON) must be selected instead.

What is the maximum allowable input voltage for the LP38690SDX-1.8?

The absolute maximum input voltage for the LP38690SDX-1.8 is 12 V, but the recommended operating range is 2.7 V to 10 V per TI's datasheet. Exceeding 10 V risks accelerated parametric drift and reduced reliability, especially at high temperature. At 10 V input and 1.8 V output delivering 1 A, power dissipation reaches 8.2 W-requiring careful thermal design using the DAP and PCB copper to maintain junction temperature below 125°C.

Can the LP38690SDX-1.8 operate with less than 1 µF output capacitance?

No-the LP38690SDX-1.8 requires a minimum 1-µF ceramic output capacitor for stability, as confirmed in the datasheet's "Typical Applications" section and "Design Requirements" table. Using smaller values (e.g., 100 nF) may cause oscillation or excessive output ripple due to insufficient phase margin. The 1-µF value is specified for X5R/X7R dielectrics with ESR between 5 mΩ and 500 mΩ; lower-ESR capacitors (e.g., COG) require series resistance per TI application guidance.

How does foldback current limiting behave on the LP38690SDX-1.8 during a short-circuit event?

During a short-circuit, the LP38690SDX-1.8's foldback current limiting reduces output current as V_OUT collapses. With VIN – VOUT > 5 V (e.g., 10 V input, near-0 V output), current is limited to ~450 mA. As VIN – VOUT drops below 4 V, the limit increases to ~1500 mA-allowing brief inrush into large capacitive loads but preventing destructive power dissipation during sustained shorts. This behavior is inherent to the IC's internal design and requires no external components.