Texas Instruments LP3982IMM-1.8

Overview

LP3982IMM-1.8 from Texas Instruments (formerly National Semiconductor) is a fixed-output 1.8V, 300mA micropower ultra-low-dropout CMOS linear regulator in an 8-pin MSOP package. It delivers 120mV typical dropout at full load, 90µA typical quiescent current, and 37µV_RMS output noise (10Hz–100kHz), enabling efficient power delivery in space-constrained, battery-powered systems such as wireless handsets and portable information appliances.

For engineers reviewing the LP3982IMM-1.8 datasheet, LP3982IMM-1.8 pinout, LP3982IMM-1.8 application, or LP3982IMM-1.8 equivalent, key selection criteria include its 1nA shutdown current, ±2% output voltage tolerance, stability with 2.2µF ceramic output capacitors, and fault detection capability via open-drain FAULT pin - all critical for low-power, high-reliability embedded designs.

Technical Context

The LP3982IMM-1.8 employs a PMOS pass transistor architecture that eliminates base drive current, enabling ultra-low quiescent current and high efficiency at light loads. Its internal bandgap reference and error amplifier provide precise regulation, while an internally generated compensation zero ensures stability with low-ESR ceramic capacitors as small as 2.2µF.

Functional block integration includes thermal overload protection, constant-current limiting, and a dedicated FAULT pin that asserts low during dropout, overcurrent, or thermal shutdown. The SHDN pin supports logic-level control with 0.4V max low threshold and 2V min high threshold, enabling seamless integration into battery-monitoring circuits.

Key Specifications

Pinout & Package

LP3982IMM-1.8 is housed in an 8-pin MSOP (Micro Small Outline Package) with 0.65mm pitch, measuring 3.0mm × 3.0mm × 1.0mm. This thermally enhanced surface-mount package supports PCB-level heat dissipation and is compatible with standard reflow profiles.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MAX8860EUB18+T, LP3982IMM-1.8 trades slightly higher quiescent current for essential fault visibility and lower output noise; versus TLS850F1BTV50, it provides higher output current and consumer-grade cost structure without automotive overhead - making it the balanced choice for portable, battery-critical designs requiring reliability and diagnostics.

Availability

LP3982IMM-1.8 is available at Aetrix Electronics and suitable for wireless handsets, DSP core power, and portable information appliances requiring stable component supply, long-term lifecycle support, and RoHS-compliant packaging.

Supply support for LP3982IMM-1.8 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 legacy analog portfolio, including precision power management ICs designed for high-performance, low-power applications.

The LP3982IMM-1.8 belongs to TI's legacy micropower LDO family, engineered specifically for battery-powered portable electronics where ultra-low IQ, low noise, and robust fault handling are essential design requirements.

FAQ

What is the maximum input voltage rating for LP3982IMM-1.8?

The absolute maximum input voltage for LP3982IMM-1.8 is 6.5V, but the recommended operating range is 2.5V to 6.0V per the datasheet. Exceeding 6.5V risks permanent damage to the internal PMOS pass transistor and bandgap reference. For reliable operation with Li-ion batteries, ensure VIN stays within specification even at full charge (typically ≤4.25V).

Does LP3982IMM-1.8 require an external feedback resistor network?

No, LP3982IMM-1.8 does not require external feedback resistors because it is a fixed-output 1.8V variant. The SET pin (Pin 8) is internally disconnected, and regulation is achieved using internal precision resistors calibrated to ±2% output tolerance. External components are limited to input/output capacitors and optional noise bypass (CCC) capacitor.

How does the FAULT pin on LP3982IMM-1.8 behave during normal operation?

During normal regulation, the FAULT pin on LP3982IMM-1.8 remains high-impedance (open-drain) and requires an external pull-up resistor (e.g., 100kΩ to VIN). It only pulls low when the device detects dropout (VIN–VOUT < threshold), overcurrent, or thermal shutdown. The pin does not assert during startup or transient load steps unless those events trigger protection.

Can LP3982IMM-1.8 operate stably with a 1µF ceramic output capacitor?

No - LP3982IMM-1.8 requires a minimum of 2.2µF ceramic output capacitance for guaranteed stability, as specified in the datasheet. Using 1µF may cause oscillation due to insufficient phase margin, especially under load transients. The internal compensation zero is optimized for ≥2.2µF, and reducing capacitance below this value invalidates stability guarantees.

What is the thermal resistance (θJA) of the LP3982IMM-1.8 MSOP package?

The junction-to-ambient thermal resistance (θJA) for LP3982IMM-1.8 in the 8-pin MSOP package is 223°C/W under natural convection (no airflow), as stated in the Absolute Maximum Ratings table. This value assumes standard JEDEC test board conditions; actual θJA improves with PCB copper area, thermal vias, and forced airflow - e.g., 182°C/W at 225 LFPM airflow.