Texas Instruments LP3990MF-1.5/NOPB

Overview

LP3990MF-1.5/NOPB from National Semiconductor is a 150mA low-noise linear voltage regulator delivering a precise 1.5V output from 2.0–6.0V input, featuring 1% voltage accuracy at room temperature, 43µA quiescent current in active mode, and <10nA shutdown current-designed for power-sensitive digital subsystems in portable electronics.

For engineers reviewing the LP3990MF-1.5/NOPB datasheet, LP3990MF-1.5/NOPB pinout, LP3990MF-1.5/NOPB application, or LP3990MF-1.5/NOPB equivalent, key selection criteria include dropout voltage (120mV typ. at 150mA), PSRR (55dB at 1kHz), fast startup time (105µs), ceramic capacitor compatibility (1.0µF min.), and thermal/short-circuit protection.

Technical Context

The LP3990MF-1.5/NOPB employs a PMOS pass transistor architecture enabling ultra-low dropout and near-zero quiescent current in shutdown. Its internal reference and error amplifier maintain regulation across −40°C to +125°C junction temperature with ±2.5% total output tolerance over line, load, and temperature.

It integrates logic-controlled enable with 0.4V low-threshold and 0.95V high-threshold, plus built-in thermal overload and short-circuit protection. Stability is guaranteed with 1.0µF ceramic output capacitors (ESR 5–500mΩ), eliminating need for noise-bypass caps.

Key Specifications

Pinout & Package

LP3990MF-1.5/NOPB uses the SOT-23-5 package (NS package code MF05A), measuring 2.9mm × 1.6mm × 1.1mm, with exposed pad for thermal dissipation. Pin 1 = VIN, Pin 2 = GND, Pin 3 = N/C, Pin 4 = N/C, Pin 5 = VOUT, and the exposed pad = GND.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar low-noise LDO applications.

Compared with LP3990MF-1.5/NOPB, the TPS7A0515PDBVR offers longer battery runtime but sacrifices dropout performance, while the ADP160ACBZ-1.5-R7 omits enable control and delivers higher noise-making LP3990MF-1.5/NOPB optimal for compact, battery-powered systems needing precise 1.5V with active power management.

Availability

LP3990MF-1.5/NOPB is available at Aetrix Electronics and suitable for smartphone baseband power, wearable sensor hubs, and industrial handheld terminals requiring stable component supply, long-term lifecycle support, and RoHS-compliant packaging.

Supply support for LP3990MF-1.5/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

National Semiconductor was a U.S.-based analog semiconductor company acquired by Texas Instruments in 2011, known for high-performance power management and precision analog ICs.

The LP3990MF-1.5/NOPB belongs to National's LDO regulator product line, engineered specifically for portable digital applications demanding low noise, low IQ, and ceramic-capacitor compatibility in ultra-small packages.

FAQ

What is the maximum input voltage rating for LP3990MF-1.5/NOPB?

The absolute maximum input voltage for LP3990MF-1.5/NOPB is 6.5V, but the recommended operating range is 2.0V to 6.0V per the Electrical Characteristics table. Exceeding 6.0V may trigger internal protection circuits or degrade long-term reliability, so designs should maintain VIN ≤ 6.0V under all conditions including transients. The LP3990MF-1.5/NOPB is commonly used with single-cell Li-ion (up to 4.2V) or dual-cell alkaline (up to 3.2V) sources.

Does LP3990MF-1.5/NOPB require an external bypass capacitor on the output?

No, LP3990MF-1.5/NOPB does not require a noise-bypass capacitor-the device achieves 125µV_RMS output noise with only a 1.0µF ceramic output capacitor. This eliminates the need for a second, smaller capacitor typically used to suppress high-frequency noise in older LDO architectures. The LP3990MF-1.5/NOPB's internal design and PMOS pass element inherently provide low noise without external bypassing.

What is the thermal resistance (θJA) of LP3990MF-1.5/NOPB in its SOT-23-5 package?

The junction-to-ambient thermal resistance (θJA) for LP3990MF-1.5/NOPB in the SOT-23-5 package is 220°C/W, as specified in the Thermal Properties section. This value assumes standard JEDEC 2-layer board conditions; actual θJA will improve with enhanced copper pour and thermal vias to the GND plane. For continuous 150mA operation at elevated ambient temperatures, thermal design must ensure junction temperature stays below 125°C using this θJA baseline.

Can LP3990MF-1.5/NOPB operate with zero load current?

Yes, LP3990MF-1.5/NOPB remains stable and in regulation with no external load-confirmed in the Application Hints section under "No-Load Stability." This capability supports CMOS RAM keep-alive circuits and always-on real-time clock (RTC) domains. The LP3990MF-1.5/NOPB maintains 1.5V output and draws only 43µA quiescent current even when I_LOAD = 0mA, making it suitable for standby power islands.

What are the enable pin voltage thresholds for LP3990MF-1.5/NOPB?

The LP3990MF-1.5/NOPB enable pin (VEN) has a low threshold (V_IL) of 0.4V max and a high threshold (V_IH) of 0.95V min, as specified in the Electrical Characteristics table. An internal 1MΩ pulldown resistor ensures default disable state. To guarantee reliable turn-on, the driving signal must exceed 0.95V; for robust noise margin, drive levels ≥1.2V are recommended. The LP3990MF-1.5/NOPB enters shutdown when VEN falls below 0.4V.