Texas Instruments LP3982IMMX-ADJ/NOPB

Overview

LP3982IMMX-ADJ/NOPB from Texas Instruments (formerly National Semiconductor) is an adjustable-output, micropower ultra low-dropout CMOS linear regulator delivering 300mA output current with 120mV typical dropout at full load, 90µA typical quiescent current, and 37µV_RMS output noise (10Hz–100kHz). It operates from 2.5V to 6.0V input and supports 1.25V–6.0V adjustable output voltage, making it ideal for battery-powered DSP core power and portable information appliances.

For engineers reviewing the LP3982IMMX-ADJ/NOPB datasheet, LP3982IMMX-ADJ/NOPB pinout, LP3982IMMX-ADJ/NOPB application, or LP3982IMMX-ADJ/NOPB equivalent, key selection criteria include its PMOS pass transistor architecture enabling near-zero drive current, internal zero compensation for stability with 2.2µF ceramic output capacitors, fault detection with open-drain FAULT pin, and shutdown mode drawing only 1nA typical supply current.

Technical Context

The LP3982IMMX-ADJ/NOPB implements a classic negative-feedback LDO topology using a 1.25V bandgap reference, error amplifier, and PMOS pass transistor - eliminating PNP base-drive current and enabling ultra-low quiescent operation. Its internal zero compensates for low-ESR ceramic capacitors, ensuring stability without external ESR requirements.

It features integrated regulation fault detection triggered by current limit, thermal shutdown, or input-to-output differential approaching dropout; the FAULT pin asserts low with 120–280mV threshold tracking load-dependent dropout voltage. Shutdown control is TTL/CMOS-compatible with 0.4V max logic-low and 2V min logic-high thresholds.

Key Specifications

Pinout & Package

LP3982IMMX-ADJ/NOPB is housed in an 8-pin MSOP package (NSC drawing MUA08A), 3.0mm × 3.0mm × 1.0mm profile, with exposed thermal pad for enhanced power dissipation (θ_JA = 223°C/W, no airflow).

Key Features

Applications

Equivalent & Alternatives

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

Compared with LP3982IMMX-ADJ/NOPB, MAX8860ETE+T offers footprint compatibility but sacrifices fault detection and ceramic-cap stability, while TLS850F0TESKXUMA1 adds automotive robustness and higher current at the cost of larger size and non-interchangeable functionality.

Availability

LP3982IMMX-ADJ/NOPB is available at Aetrix Electronics and suitable for wireless handsets, DSP core power, and battery-powered electronics requiring stable component supply, long-term lifecycle support, and RoHS-compliant packaging.

Supply support for LP3982IMMX-ADJ/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 acquired National Semiconductor in 2011 and maintains its precision analog and power management portfolio, serving industrial, automotive, and portable electronics markets globally.

The LP3982IMMX-ADJ/NOPB belongs to TI's legacy micropower LDO family, engineered specifically for ultra-low-noise, ultra-low-quiescent-power regulation in space-constrained, battery-critical applications.

FAQ

What is the minimum output capacitance required for stable operation of the LP3982IMMX-ADJ/NOPB?

The LP3982IMMX-ADJ/NOPB is stable with a minimum 2.2µF ceramic output capacitor. This value is validated across temperature and load conditions per the datasheet, and no ESR requirement applies due to internal zero compensation. Larger values (e.g., 10µF) improve transient response but are not necessary for stability. Using less than 2.2µF risks oscillation or poor regulation.

How does the FAULT pin on the LP3982IMMX-ADJ/NOPB function, and what external components are needed?

FAULT is an open-drain output that pulls low during overcurrent, thermal shutdown, or when input-to-output differential drops within ~100mV of dropout. It requires an external pull-up resistor - typically 100kΩ to VOUT or system rail - to avoid excessive current draw. The FAULT threshold tracks load-dependent dropout voltage, providing early warning before regulation loss. No additional passive components are required beyond the pull-up.

Can the LP3982IMMX-ADJ/NOPB be used with a 1.5V input supply?

No, the LP3982IMMX-ADJ/NOPB has a minimum input voltage of 2.5V per Absolute Maximum Ratings and Operating Conditions. At 1.5V input, the device will not regulate and may enter undefined behavior or fail to power up. For sub-2.5V inputs, consider alternative regulators such as the TPS7A05 (1.4V min VIN) or TLV700 series.

What is the purpose of the CC pin on the LP3982IMMX-ADJ/NOPB, and what capacitor value is recommended?

The CC pin connects to the internal bandgap reference node and accepts a noise-bypass capacitor to reduce output voltage noise. A 33nF NPO or COG ceramic capacitor is recommended - this value optimally balances noise reduction (~20dB improvement) and start-up time. Smaller values speed turn-on but reduce noise suppression; larger values increase turn-on delay without significant noise benefit.

Is the LP3982IMMX-ADJ/NOPB pin-compatible with the MAX8860, and are there functional differences?

Yes, the LP3982IMMX-ADJ/NOPB is explicitly stated as pin-, package-, and specification-compatible with Maxim's MAX8860 for the adjustable version. However, key functional differences exist: LP3982IMMX-ADJ/NOPB includes FAULT detection and internal zero compensation for ceramic capacitors, while MAX8860 lacks both features and requires higher-ESR output capacitors. They are not drop-in replacements where fault signaling or 2.2µF ceramic stability is required.