Texas Instruments LP3981ILDX-2.8/NOPB

Overview

LP3981ILDX-2.8/NOPB from Texas Instruments is a micropower, ultra-low-dropout CMOS voltage regulator delivering 300 mA at fixed 2.8 V output, with 132 mV typical dropout at full load, 35 µV_RMS output noise (10 Hz–100 kHz), and ≤1 µA shutdown quiescent current. It serves as the primary power supply for RF front-end ICs and baseband processors in battery-powered cellular handsets.

For engineers reviewing the LP3981ILDX-2.8/NOPB datasheet, LP3981ILDX-2.8/NOPB pinout, LP3981ILDX-2.8/NOPB application, or LP3981ILDX-2.8/NOPB equivalent, key selection criteria include dropout performance under 300-mA load, ceramic-capacitor stability (2.2 µF min), EN-controlled shutdown leakage (<1.5 µA), and PSRR >55 dB at 10 kHz in compact WSON-6 packaging.

Technical Context

The LP3981ILDX-2.8/NOPB employs a PMOS pass transistor architecture enabling ultra-low dropout and minimal ground current increase in dropout-critical for extending battery runtime in portable devices. Its internal bandgap reference (1.23 V) feeds a precision error amplifier that regulates output via OUT-SENSE feedback, supporting remote sensing for improved load regulation.

It integrates logic-controlled enable (VIH = 1.4 V, VIL = 0.4 V), thermal shutdown (160°C), and short-circuit current limiting (600 mA). The BYPASS pin connects to an external 0.033 µF capacitor to reduce reference noise without degrading transient response-enabling low-noise operation essential for sensitive analog/RF circuitry.

Key Specifications

Pinout & Package

LP3981ILDX-2.8/NOPB is packaged in a thermally enhanced 6-pin WSON (NGC) package measuring 4.00 mm × 3.00 mm with exposed thermal pad (connected to GND). This package delivers R_θJA = 56.5°C/W-enabling high-power-density designs without heatsinks.

Key Features

Applications

Equivalent & Alternatives

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

Compared with TPL7407LPGEDR and MCP1703T-2802E/MB, LP3981ILDX-2.8/NOPB uniquely combines 300 mA capability, 132 mV dropout, 35 µV_RMS noise with BYPASS, and OUT-SENSE feedback-making it the only option meeting full RF front-end and high-efficiency battery runtime requirements simultaneously.

Availability

LP3981ILDX-2.8/NOPB is available at Aetrix Electronics and suitable for CDMA handset design, WCDMA RF module integration, and portable information appliance production requiring stable component supply, long-term lifecycle support, and TI-authorized traceability.

Supply support for LP3981ILDX-2.8/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 designing analog ICs, embedded processors, and connectivity solutions for industrial, automotive, and consumer markets since 1930.

The LP3981 family was engineered specifically for battery-powered wireless infrastructure and handsets-delivering micropower efficiency, ultra-low noise, and ceramic-capacitor compatibility in miniature WSON packaging.

FAQ

What is the minimum input voltage required for LP3981ILDX-2.8/NOPB to regulate at full 300 mA load?

The LP3981ILDX-2.8/NOPB requires VIN ≥ VOUT + dropout voltage to maintain regulation. With 132 mV typical dropout at 300 mA, the minimum functional input is 2.8 V + 0.132 V = 2.932 V. At lower inputs, output voltage sags below 2.8 V; datasheet specifies operation only down to VIN = 2.7 V, but full-load regulation is not guaranteed below 2.932 V.

Can LP3981ILDX-2.8/NOPB operate without the BYPASS capacitor?

Yes, LP3981ILDX-2.8/NOPB functions without the BYPASS capacitor, but output noise increases from 35 µV_RMS to approximately 85 µV_RMS. The BYPASS pin is optional-omitting it simplifies BOM but compromises noise performance critical for RF and precision analog circuits powered by LP3981ILDX-2.8/NOPB.

Is the OUT-SENSE pin mandatory for LP3981ILDX-2.8/NOPB operation?

Yes, the OUT-SENSE pin must be connected directly to the OUT pin for proper regulation. The LP3981ILDX-2.8/NOPB uses this connection to close the feedback loop; leaving it unconnected or routing it separately causes output voltage inaccuracy and potential instability. This requirement applies regardless of PCB layout or trace length.

What is the maximum allowable junction temperature for LP3981ILDX-2.8/NOPB, and how is thermal protection implemented?

The LP3981ILDX-2.8/NOPB has a thermal shutdown threshold of 160°C with 20°C hysteresis. When junction temperature exceeds 160°C, the device disables output and draws <1.5 µA until temperature falls to ~140°C, then resumes regulation. This protects against permanent damage during sustained overload or inadequate PCB copper area in the WSON-6 thermal pad layout.

Does LP3981ILDX-2.8/NOPB support ceramic output capacitors smaller than 2.2 µF?

No-LP3981ILDX-2.8/NOPB requires a minimum 2.2 µF ceramic output capacitor for guaranteed stability, as validated in TI's characterization. Using smaller values (e.g., 1 µF) may cause oscillation or poor transient response. The datasheet explicitly specifies 2.2–22 µF range with 5–500 mΩ ESR; deviation risks violating stability criteria defined for the WSON-6 package.