Texas Instruments LP3981IMM-2.7

Overview

LP3981IMM-2.7 from Texas Instruments is a micropower, ultra-low-dropout CMOS voltage regulator delivering 300 mA at fixed 2.7 V output, optimized for battery-powered wireless systems. It features 132 mV typical dropout at full load, ≤1 µA shutdown quiescent current, and 35 µV_RMS output noise (10 Hz–100 kHz), enabling clean power in CDMA/GSM handset RF sections.

For engineers reviewing the LP3981IMM-2.7 datasheet, LP3981IMM-2.7 pinout, LP3981IMM-2.7 application, or LP3981IMM-2.7 equivalent, key selection criteria include dropout performance under low VIN, PSRR at 1 kHz, ceramic capacitor stability, thermal resistance in WSON-6, and EN logic thresholds for low-power sequencing.

Technical Context

The LP3981IMM-2.7 uses a CMOS pass transistor architecture with internal bandgap reference (1.23 V) and fast-turnon circuitry to achieve 120–240 µs enable response. Its feedback loop employs OUT-SENSE for remote sensing, requiring direct connection to OUT to maintain regulation accuracy.

It integrates thermal shutdown (160°C trip, 20°C hysteresis) and short-circuit current limiting (600 mA), while maintaining 60 dB PSRR at 1 kHz across 2.7–6 V input range and −40°C to +125°C operating temperature.

Key Specifications

Pinout & Package

LP3981IMM-2.7 is packaged in a 6-pin WSON (NGC) package measuring 4.00 mm × 3.00 mm with exposed thermal pad (pin 4). This thermally enhanced layout enables 56.5°C/W junction-to-ambient resistance, supporting high-current operation without external heatsinking.

Key Features

Applications

Equivalent & Alternatives

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

Compared with TPL7407LDR and MCP1703T-2702E/MB, LP3981IMM-2.7 delivers superior noise suppression and lower dropout-critical for RF and high-precision analog systems-while maintaining identical 6-pin WSON footprint and enable logic compatibility.

Availability

LP3981IMM-2.7 is available at Aetrix Electronics and suitable for CDMA/GSM handset power management, portable medical sensor analog rails, and WLAN/BT combo module reference supplies requiring stable component supply, long-term lifecycle support, and consistent parametric performance across production batches.

Supply support for LP3981IMM-2.7 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 solutions for industrial, automotive, and communications markets.

The LP3981 family was engineered specifically for battery-powered wireless infrastructure and mobile devices, emphasizing ultra-low noise, micropower shutdown, and ceramic-capacitor compatibility to reduce bill-of-materials and PCB area.

FAQ

What is the minimum input voltage required for LP3981IMM-2.7 to regulate at full 300 mA load?

The LP3981IMM-2.7 requires VIN ≥ VOUT + dropout voltage to maintain regulation. With 132 mV typical dropout at 300 mA, the minimum functional input is 2.832 V. The datasheet specifies 2.7 V as absolute minimum VIN, but operation below 2.83 V risks output droop under full load. Always verify with worst-case dropout (200 mV) across temperature for robust design.

Can LP3981IMM-2.7 operate without the BYPASS capacitor, and what is the impact on noise performance?

Yes, LP3981IMM-2.7 functions without the BYPASS capacitor, but output noise increases significantly-from 35 µV_RMS to approximately 120 µV_RMS (typical, 10 Hz–100 kHz). The BYPASS pin connects to a high-impedance reference node; omitting the 0.033 µF capacitor removes noise filtering, degrading SNR in RF and precision analog applications.

Is the OUT-SENSE pin mandatory for LP3981IMM-2.7 operation, and how should it be connected?

Yes, the OUT-SENSE pin is mandatory. Per TI's datasheet, OUT-SENSE (Pin 3) must be directly connected to the OUT pin (Pin 1) using a low-impedance trace or short wire. This connection enables remote-sense feedback, ensuring accurate 2.7 V regulation at the load despite PCB trace resistance. Leaving OUT-SENSE unconnected or routing it separately causes output voltage error and instability.

What thermal considerations apply to LP3981IMM-2.7 in the WSON-6 package at 300 mA load?

At 300 mA and 2.7 V output with 3.5 V input, LP3981IMM-2.7 dissipates ~240 mW. With R_θJA = 56.5°C/W, junction temperature rise is ~13.6°C above ambient. To stay within the 125°C max junction limit, ambient must remain ≤111°C. Use the exposed thermal pad (Pin 4) soldered to ≥100 mm² copper pour for reliable operation at full load across industrial temperature range.

Does LP3981IMM-2.7 support ceramic output capacitors smaller than 2.2 µF, and what is the minimum stable value?

No-TI specifies 2.2 µF as the minimum stable output capacitance for LP3981IMM-2.7. Using <2.2 µF (e.g., 1 µF) violates stability criteria and may cause oscillation or poor transient response. The device is characterized for 2.2–22 µF ceramic capacitors with 5–500 mΩ ESR; values outside this range risk regulation failure, especially under dynamic load conditions.