Texas Instruments LP3981ILDX-2.5/NOPB

Overview

LP3981ILDX-2.5/NOPB from Texas Instruments is a micropower, ultra-low-dropout CMOS voltage regulator delivering 300 mA at fixed 2.5 V output, with 132 mV typical dropout at full load, ≤1 µA shutdown current, and 35 µV_RMS output noise (10 Hz–100 kHz). It serves as the primary power rail for RF front-end ICs and baseband processors in battery-powered cellular handsets.

For engineers reviewing the LP3981ILDX-2.5/NOPB datasheet, LP3981ILDX-2.5/NOPB pinout, LP3981ILDX-2.5/NOPB application, or LP3981ILDX-2.5/NOPB equivalent, key selection criteria include dropout performance under 300-mA load, PSRR >60 dB at 1 kHz, ceramic-capacitor stability, thermal resistance in WSON-6, and enable-controlled shutdown leakage <1.5 µA.

Technical Context

The LP3981ILDX-2.5/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 driving the pass device, with fast turnon circuitry reducing t_ON to 240 µs (typical) using a 0.033 µF BYPASS capacitor.

It integrates thermal shutdown (160°C trip, 20°C hysteresis) and short-circuit current limiting (600 mA), operates across −40°C to +125°C, and maintains 60 dB PSRR down to input voltages as low as V_OUT + 0.3 V - critical for declining battery operation in CDMA/GSM handsets.

Key Specifications

Pinout & Package

LP3981ILDX-2.5/NOPB is packaged in a thermally enhanced 6-pin WSON (NGC) package measuring 4.00 mm × 3.00 mm with exposed thermal pad (pin 4 = GND). The package delivers R_θJA = 56.5°C/W and R_θJB = 30.9°C/W, enabling high-power-density layouts in space-constrained mobile PCBs.

Key Features

Applications

Equivalent & Alternatives

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

Compared with TLS850F2BHTSA1 and MCP1826T-2502E/DB, LP3981ILDX-2.5/NOPB offers the lowest combination of dropout (132 mV), noise (35 µV_RMS), and shutdown current (≤1.5 µA), making it uniquely suited for high-performance, battery-limited RF and portable computing applications where efficiency and signal integrity are co-prioritized.

Availability

LP3981ILDX-2.5/NOPB is available at Aetrix Electronics and suitable for CDMA handset design, portable information appliance development, and GSM baseband power management requiring stable component supply, long-term lifecycle support, and traceable sourcing.

Supply support for LP3981ILDX-2.5/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 company designing analog ICs, embedded processors, and system-on-chip solutions for industrial, automotive, and consumer markets.

The LP3981ILDX-2.5/NOPB belongs to TI's micropower LDO family engineered specifically for battery-powered wireless devices, emphasizing ultra-low noise, minimal dropout, and sub-µA shutdown to maximize runtime in compact form factors.

FAQ

What is the maximum input voltage rating for LP3981ILDX-2.5/NOPB?

The absolute maximum input voltage for LP3981ILDX-2.5/NOPB is 6.5 V, but recommended operating conditions specify VIN ≤ 6 V. Exceeding 6 V risks permanent damage per Absolute Maximum Ratings. For reliable operation across temperature, maintain VIN between 2.7 V and 6 V, with minimum headroom of V_OUT + 0.3 V (i.e., ≥2.8 V) to ensure regulation. The LP3981ILDX-2.5/NOPB is not rated for automotive 12-V or industrial 24-V input rails.

Can LP3981ILDX-2.5/NOPB operate stably with a 1-µF ceramic output capacitor?

No - LP3981ILDX-2.5/NOPB requires a minimum 2.2 µF ceramic output capacitor for guaranteed stability, as specified in Electrical Characteristics and Application section 9.2.2.4. Using 1 µF violates the design requirement and may cause oscillation or poor transient response. Acceptable capacitors include X7R, Y5V, or Z5U dielectrics in the 2.2–22 µF range with ESR between 5 mΩ and 500 mΩ. The LP3981ILDX-2.5/NOPB is not characterized for 1-µF operation.

Does LP3981ILDX-2.5/NOPB require the OUT-SENSE pin to be connected externally?

Yes - the OUT-SENSE pin (Pin 3) must be connected directly to the OUT pin (Pin 1) using a short, low-impedance trace. This connection is mandatory for proper regulation and load transient performance. Leaving OUT-SENSE floating or connecting it elsewhere invalidates the output voltage accuracy and may cause instability. The LP3981ILDX-2.5/NOPB uses this sense path to compensate for IR drop in PCB traces, achieving tighter load regulation (±0.005%/mA).

What is the thermal performance difference between WSON and VSSOP packages for LP3981ILDX-2.5/NOPB?

The WSON-6 package (used in LP3981ILDX-2.5/NOPB) provides significantly better thermal performance than the VSSOP-8 option: R_θJA = 56.5°C/W vs. 177°C/W, and R_θJB = 30.9°C/W vs. 97.4°C/W. This allows the LP3981ILDX-2.5/NOPB to dissipate ~3× more power at the same ambient temperature. The exposed thermal pad in WSON must be soldered to a dedicated PCB ground plane to realize this advantage - the LP3981ILDX-2.5/NOPB cannot achieve its rated 300-mA capability in high-ambient environments without proper thermal layout.

Is LP3981ILDX-2.5/NOPB compatible with tantalum output capacitors?

Yes - LP3981ILDX-2.5/NOPB is stable with high-quality tantalum output capacitors, provided they meet the 2.2–22 µF capacitance range and 5–500 mΩ ESR specification. However, ceramic capacitors are strongly preferred due to lower cost, smaller size, and superior ESR consistency over temperature. Tantalum ESR can double from 25°C to −40°C, risking instability at cold temperatures unless oversized - the LP3981ILDX-2.5/NOPB datasheet explicitly recommends ceramic for robustness across the full −40°C to +125°C range.