Texas Instruments LP3981IMM-2.8/NOPB

Overview

LP3981IMM-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 a precision power supply for RF and analog circuitry in battery-powered mobile handsets.

For engineers reviewing the LP3981IMM-2.8/NOPB datasheet, LP3981IMM-2.8/NOPB pinout, LP3981IMM-2.8/NOPB application, or LP3981IMM-2.8/NOPB equivalent, key selection criteria include its WSON-6 package thermal resistance (R_θJB = 30.9 °C/W), logic-controlled enable interface, ceramic-capacitor stability (2.2 µF min), and PSRR >55 dB at 10 kHz under 50 mA load.

Technical Context

The LP3981IMM-2.8/NOPB employs a CMOS pass transistor architecture with internal bandgap reference (1.23 V) and fast-turnon circuitry to achieve 240 µs typical enable response. Its OUT-SENSE pin enables remote sensing for improved load regulation accuracy, requiring direct connection to the OUT pin in standard configurations.

It integrates thermal shutdown (160 °C trip, 20 °C hysteresis) and short-circuit current limiting (600 mA steady-state), operating across −40 °C to +125 °C with input range 2.7 V–6 V. The BYPASS pin accepts a 0.033 µF capacitor to reduce reference noise without degrading transient response.

Key Specifications

Pinout & Package

LP3981IMM-2.8/NOPB is packaged in a 6-pin WSON (NGC) with 4.00 mm × 3.00 mm body size and exposed thermal pad connected to GND. The package provides low thermal resistance (R_θJB = 30.9 °C/W) for high-current operation 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 LP3981IMM-2.8/NOPB, TPL7407LPGP offers smaller footprint but sacrifices dropout performance and protection features, while MCP1700T-2802E/MB trades current capability and sensing flexibility for lower unit cost and simpler layout.

Availability

LP3981IMM-2.8/NOPB is available at Aetrix Electronics and suitable for CDMA handset power management, RF transceiver biasing, portable information appliance core logic, and GSM audio codec supply requiring stable component supply, full production traceability, and long-term lifecycle support.

Supply support for LP3981IMM-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 specializing in analog and embedded processing technologies, with leadership in power management ICs and high-reliability signal chain solutions.

The LP3981 family was designed specifically for ultra-low-noise, micropower battery-powered wireless applications-including cellular handsets and portable information appliances-where dropout voltage, quiescent current, and output stability are critical.

FAQ

What is the minimum input voltage required for LP3981IMM-2.8/NOPB to maintain regulation?

The LP3981IMM-2.8/NOPB requires VIN ≥ VOUT + 0.3 V for proper operation, meaning a minimum input of 3.1 V under nominal conditions. At 300 mA load, its 132 mV typical dropout allows regulation down to 2.932 V input, but the datasheet specifies 2.7 V as the absolute minimum recommended input voltage across temperature.

Can LP3981IMM-2.8/NOPB operate without the BYPASS capacitor?

Yes, LP3981IMM-2.8/NOPB functions without the BYPASS capacitor, delivering 2.8 V output with standard LDO performance. However, omitting the 0.033 µF capacitor increases output noise to ~75 µV_RMS; the BYPASS pin is optional but essential for applications requiring 35 µV_RMS noise performance, such as RF VCO supplies.

Is the OUT-SENSE pin mandatory for LP3981IMM-2.8/NOPB operation?

Yes-the OUT-SENSE pin must be connected directly to the OUT pin in all standard configurations. This connection enables the internal error amplifier to regulate based on the actual load voltage, compensating for PCB trace resistance. Leaving OUT-SENSE unconnected or routing it separately invalidates regulation accuracy and may cause instability.

What thermal considerations apply to LP3981IMM-2.8/NOPB in WSON-6 package?

LP3981IMM-2.8/NOPB in WSON-6 has R_θJB = 30.9 °C/W and R_θJA = 56.5 °C/W (High-K board). At 300 mA and 3.5 V input, power dissipation is ~210 mW; with 25 °C ambient, junction temperature rises ~6.5 °C above ambient with proper PCB copper pour-well below the 125 °C max rating. Thermal pad soldering to solid ground plane is mandatory.

Does LP3981IMM-2.8/NOPB support ceramic output capacitors below 2.2 µF?

No-TI specifies a minimum 2.2 µF ceramic output capacitor (X7R/Z5U/Y5V, 5–500 mΩ ESR) for guaranteed stability. Using smaller values risks oscillation or poor transient response. The device is optimized for 2.2–22 µF range; 1 µF ceramics fall outside validated design space and are not recommended for LP3981IMM-2.8/NOPB.