Texas Instruments LP3990SD-1.35/NOPB

Overview

LP3990SD-1.35/NOPB from National Semiconductor is a 150mA low-noise linear voltage regulator delivering a precise 1.35V output from 2.0–6.0V input, featuring 43µA quiescent current in active mode, <10nA shutdown current, and stability with 1.0µF ceramic capacitors. It serves as a power supply for core logic and I/O rails in portable digital systems requiring tight voltage accuracy and minimal board space.

For engineers reviewing the LP3990SD-1.35/NOPB datasheet, LP3990SD-1.35/NOPB pinout, LP3990SD-1.35/NOPB application, or LP3990SD-1.35/NOPB equivalent, key selection criteria include dropout voltage (120mV typ. at 150mA), PSRR (55dB @ 1kHz), fast startup (105µs), thermal/short-circuit protection, and LLP-6 package compatibility with SOT23 footprint.

Technical Context

The LP3990SD-1.35/NOPB employs a PMOS pass transistor architecture enabling ultra-low dropout and near-zero quiescent current in shutdown. Its internal bandgap reference and error amplifier deliver ±1.5% output voltage tolerance over −40°C to +125°C junction temperature.

Designed for digital load transients, it achieves 55mV peak-to-peak load step response (1mA → 150mA) with 1µF output capacitance and maintains stability without noise-bypass capacitors due to integrated low-noise design and 150µV_RMS output noise.

Key Specifications

Pinout & Package

LP3990SD-1.35/NOPB is housed in a lead-free LLP-6 (SOT23 footprint) package measuring 2.0mm × 2.2mm × 0.8mm, with exposed thermal pad for enhanced power dissipation (θ_JA = 88°C/W).

Key Features

Applications

Equivalent & Alternatives

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

Compared with LP3990SD-1.35/NOPB, the XC6219B132MR-G trades thermal safety and precision for lower IQ, while the AP7361-C-13-SAG-7 offers current headroom at the expense of voltage accuracy and integrated control - making LP3990SD-1.35/NOPB optimal for space-constrained, battery-sensitive digital loads demanding guaranteed 1.35V ±1.5% and autonomous fault protection.

Availability

LP3990SD-1.35/NOPB is available at Aetrix Electronics and suitable for portable medical monitors, industrial handheld terminals, smartphone baseband modules, and wearable sensor hubs requiring stable component supply across extended temperature ranges and long production lifecycles.

Supply support for LP3990SD-1.35/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 semiconductor company specializing in analog and power management ICs, acquired by Texas Instruments in 2011; its LDO portfolio remains widely deployed in industrial and portable electronics.

The LP3990 series was designed specifically for digital applications in battery-powered systems, emphasizing ultra-low quiescent current, ceramic-capacitor compatibility, and robust protection features without sacrificing voltage accuracy or noise performance.

FAQ

What is the maximum input voltage rating for LP3990SD-1.35/NOPB?

The absolute maximum input voltage for LP3990SD-1.35/NOPB is 6.5V, but the recommended operating range is 2.0V to 6.0V. Exceeding 6.5V risks permanent damage to the internal PMOS pass device and bandgap reference circuitry. For reliable operation in battery-fed systems, VIN should remain within specification even during charging surges or cold-cranking events.

Does LP3990SD-1.35/NOPB require an external pull-down resistor on the enable pin?

No - LP3990SD-1.35/NOPB integrates a 1MΩ internal pulldown resistor on the VEN pin, ensuring the device remains disabled during power-up or when the enable signal is floating. This eliminates the need for an external resistor and simplifies PCB layout, especially in space-constrained portable designs where every mm² counts.

Can LP3990SD-1.35/NOPB operate with a 0.47µF output capacitor?

No - LP3990SD-1.35/NOPB requires a minimum 0.7µF output capacitance (1.0µF recommended) with ESR between 5mΩ and 500mΩ for guaranteed stability. Using 0.47µF violates the specified minimum and may cause oscillation or poor transient response, particularly under load steps from 1mA to 150mA. Always verify capacitor DC bias derating per manufacturer datasheets.

What is the thermal resistance (θJA) of LP3990SD-1.35/NOPB in its LLP-6 package?

The junction-to-ambient thermal resistance (θJA) for LP3990SD-1.35/NOPB in the LLP-6 package is 88°C/W under standard JEDEC test conditions (2-layer board, 1-in² copper). Actual θJA depends on PCB layout - adding thermal vias under the exposed pad and increasing copper area can reduce it to ~50°C/W, enabling full 150mA output at ambient temperatures up to 85°C.

Is LP3990SD-1.35/NOPB RoHS-compliant and lead-free?

Yes - LP3990SD-1.35/NOPB is manufactured in a lead-free process and complies with RoHS Directive 2011/65/EU. The "/NOPB" suffix explicitly denotes lead-free packaging, and the device uses matte tin plating on all terminations. It is also halogen-free and compliant with IPC/JEDEC J-STD-020 moisture sensitivity level 1 (MSL-1) for unlimited floor life.