Texas Instruments LP3982IMMX-ADJ

Overview

LP3982IMMX-ADJ 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 output voltage adjustment from 1.25V to 6.0V via external resistor divider - ideal for DSP core power and battery-powered portable electronics requiring stable low-noise bias.

For engineers reviewing the LP3982IMMX-ADJ datasheet, LP3982IMMX-ADJ pinout, LP3982IMMX-ADJ application, or LP3982IMMX-ADJ equivalent, key selection criteria include its PMOS pass transistor architecture enabling ultra-low IQ and shutdown current (1nA), ceramic-capacitor stability (≥2.2µF), FAULT pin for regulation monitoring, and MSOP-8 package compatibility with MAX8860.

Technical Context

The LP3982IMMX-ADJ implements a PMOS-based LDO topology with internal 1.25V bandgap reference and error amplifier, enabling high open-loop gain and precise output regulation. Its feedback loop incorporates an internally generated zero to ensure stability with low-ESR ceramic capacitors as small as 2.2µF - eliminating reliance on capacitor ESR for compensation.

It integrates fault detection (open-drain FAULT pin active low during dropout, overcurrent, or thermal shutdown), logic-controlled shutdown (SHDN pin with 0.4V max low threshold), and fast 120µs turn-on time using an internal 500µA charge current source. The SET pin accepts external resistive divider for output voltage programming while maintaining ±2% tolerance across load (100µA–300mA) and temperature (−40°C to +85°C).

Key Specifications

Pinout & Package

LP3982IMMX-ADJ is packaged in an 8-pin MSOP (NSC drawing MUA08A), 3.0mm × 3.0mm × 1.0mm body, exposed pad optional for thermal enhancement. Pinout validated per National Semiconductor DS200369 (March 2006) and TI replacement documentation.

Key Features

Applications

Equivalent & Alternatives

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

Compared with LP3982IMMX-ADJ, MAX8860EUB+T offers mechanical compatibility but sacrifices noise performance and fault visibility, while TLS850F0TESA1 provides automotive robustness at the cost of programmability and system-level diagnostics - making LP3982IMMX-ADJ the optimal choice for portable, battery-constrained, noise-sensitive designs requiring full status monitoring.

Availability

LP3982IMMX-ADJ is available at Aetrix Electronics and suitable for wireless handset power, DSP core bias, and portable instrumentation requiring stable component supply, long-term lifecycle continuity, and RoHS-compliant packaging.

Supply support for LP3982IMMX-ADJ 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 full technical and supply chain support for legacy National products including the LP3982 series.

The LP3982IMMX-ADJ belongs to National's micropower LDO family designed specifically for battery-powered portable electronics demanding ultra-low IQ, low-noise regulation, and ceramic-capacitor compatibility in space-constrained MSOP packages.

FAQ

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

The LP3982IMMX-ADJ is stable with a minimum 2.2µF ceramic output capacitor (X5R or X7R dielectric). This value is validated across temperature and load conditions per DS200369. Using smaller capacitors risks instability due to insufficient phase margin, while larger values (e.g., 10µF) are acceptable but offer diminishing returns in noise suppression. The 2.2µF requirement enables compact, low-cost designs without tantalum or electrolytic components.

How does the FAULT pin on the LP3982IMMX-ADJ function, and what conditions trigger it?

The FAULT pin on the LP3982IMMX-ADJ is an open-drain output that pulls low during three conditions: (1) input-to-output differential falls below the tracked dropout threshold, (2) thermal shutdown activates at ~160°C junction temperature, or (3) current limit is reached (~330–770mA). It remains low until all fault conditions clear and the regulator re-stabilizes. A 100kΩ pull-up resistor to system rail is required for proper logic-level interfacing with microcontrollers or PMICs.

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

No - the LP3982IMMX-ADJ has a minimum input voltage rating of 2.5V per Absolute Maximum Ratings and Operating Conditions tables. Operation below 2.5V violates guaranteed specifications and may result in unregulated output, increased dropout, or failure to start. For sub-2.5V inputs, consider dedicated ultra-low-input LDOs such as TPS7A05 (1.8V min VIN) or AP2204 (1.8V min VIN), which are not pin-compatible with LP3982IMMX-ADJ.

What is the purpose of the CC pin (Pin 6) on the LP3982IMMX-ADJ, and what capacitor value is recommended?

The CC pin on the LP3982IMMX-ADJ connects directly to the internal bandgap reference and accepts a noise-bypass capacitor to reduce output voltage noise. A 33nF NPO or COG ceramic capacitor is specified as optimal in DS200369 - this value reduces RMS noise from 37µV to <25µV while maintaining fast 120µs turn-on time. Larger values increase turn-on delay; smaller values provide less noise attenuation. Leakage current must remain below 1nA to avoid reference loading and output voltage error.

Is the LP3982IMMX-ADJ RoHS compliant and lead-free?

Yes - the LP3982IMMX-ADJ is RoHS compliant and lead-free per National Semiconductor's Banned Substances Specification (CSP-9-111S2) and TI's current product declarations. The MSOP-8 package uses matte tin lead finish and conforms to JEDEC J-STD-020 moisture sensitivity level 1 (MSL-1), allowing unlimited floor life at ≤30°C/60% RH. Full compliance documentation is available through TI's product page for SNPS3982 (TI's cross-reference part number).