Texas Instruments LP3981ILD-2.8/NOPB

Overview

LP3981ILD-2.8/NOPB from Texas Instruments is a fixed-output, ultra-low-dropout CMOS voltage regulator delivering 300 mA at 2.8 V with 132 mV typical dropout (300 mA load), ≤1 µA shutdown quiescent current, and 35 µV_RMS output noise (10 Hz–100 kHz). It serves as the primary power rail for RF front-end and baseband ICs in cellular handsets.

For engineers reviewing the LP3981ILD-2.8/NOPB datasheet, LP3981ILD-2.8/NOPB pinout, LP3981ILD-2.8/NOPB application, or LP3981ILD-2.8/NOPB equivalent, key selection criteria include dropout voltage under full load, PSRR at 1 kHz, thermal resistance in WSON-6, BYPASS pin noise-reduction capability, and EN logic thresholds across temperature.

Technical Context

The LP3981ILD-2.8/NOPB employs a PMOS pass transistor architecture enabling ultra-low dropout and minimal ground current increase in dropout. Its internal bandgap reference (1.23 V) feeds a precision error amplifier that drives the pass element via fast-turnon circuitry, achieving 240 µs typical enable response with 0.033 µF BYPASS capacitor.

It integrates thermal shutdown (160°C trip, 20°C hysteresis) and short-circuit current limiting (600 mA steady-state). The OUT-SENSE pin provides remote sensing capability but must be tied directly to OUT for standard operation; the WSON-6 package includes an exposed thermal pad connected to GND for low R_θJB (30.9°C/W).

Key Specifications

Pinout & Package

The LP3981ILD-2.8/NOPB is housed in a 6-pin WSON package (4.00 mm × 3.00 mm) with exposed thermal pad. Pin 1 is OUT; pin 2 is IN; pin 3 is OUT-SENSE; pin 4 is GND (connected to thermal pad); pin 5 is BYPASS; pin 6 is EN.

Key Features

Applications

Equivalent & Alternatives

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

Compared with LP3981ILD-2.8/NOPB, TPL7407LDR trades noise performance for simplified layout (no BYPASS net), while MCP1826T-2802E/DB sacrifices dropout and PSRR for broader vendor availability and lower unit cost-neither matches LP3981ILD-2.8/NOPB's combination of 132-mV dropout, 60-dB PSRR, and 35-µV_RMS noise in WSON-6.

Availability

LP3981ILD-2.8/NOPB is available at Aetrix Electronics and suitable for CDMA/WCDMA handset design, portable medical monitors, and industrial handheld terminals requiring stable component supply, long-term lifecycle assurance, and traceable sourcing.

Supply support for LP3981ILD-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 company headquartered in Dallas, Texas, specializing in analog and embedded processing technologies with broad manufacturing scale and automotive/industrial qualification expertise.

The LP3981ILD-2.8/NOPB belongs to TI's micropower LDO family engineered specifically for battery-powered wireless infrastructure and mobile devices where ultra-low dropout, low noise, and minimal quiescent current are mandatory.

FAQ

What is the minimum input voltage required for LP3981ILD-2.8/NOPB to maintain regulation?

The LP3981ILD-2.8/NOPB requires VIN ≥ VOUT + 0.3 V for proper operation, meaning a minimum input of 3.1 V is needed to guarantee 2.8 V output regulation. However, its 132 mV typical dropout at 300 mA allows functional regulation down to 2.93 V input-critical for extending runtime in single-cell Li-ion systems nearing end-of-discharge.

Can LP3981ILD-2.8/NOPB operate without the BYPASS capacitor?

Yes, LP3981ILD-2.8/NOPB functions without the BYPASS capacitor but delivers higher output noise-35 µV_RMS is only achieved with a 0.033 µF capacitor on the BYPASS pin. Omitting it increases RMS noise and degrades PSRR at higher frequencies; the device remains stable and fully operational, just with reduced noise performance.

Is the OUT-SENSE pin mandatory for LP3981ILD-2.8/NOPB operation?

No, the OUT-SENSE pin is not mandatory. For standard local regulation, OUT-SENSE must be shorted directly to the OUT pin. It is only used for remote sensing when routing losses between the LDO and load require compensation-otherwise, leaving it unconnected or floating is invalid and may cause instability or incorrect regulation.

What thermal performance can be expected from LP3981ILD-2.8/NOPB in the WSON-6 package?

In the WSON-6 package, LP3981ILD-2.8/NOPB achieves R_θJB = 30.9°C/W and R_θJA = 56.5°C/W (JEDEC High-K board). With 25°C ambient and full 300 mA load at 2.8 V output, junction temperature rise is ~52°C-well within the −40°C to +125°C operating range. Proper PCB copper pour under the thermal pad is essential to realize this rating.

Does LP3981ILD-2.8/NOPB support ceramic output capacitors below 2.2 µF?

No-TI specifies 2.2 µF as the minimum ceramic output capacitance for LP3981ILD-2.8/NOPB stability. Using smaller values (e.g., 1 µF) risks oscillation or poor transient response. The device is validated for 2.2–22 µF ceramic capacitors with 5–500 mΩ ESR; X7R dielectric is recommended for stable capacitance across temperature.