Texas Instruments LP3991TL-1.5/NOPB

Overview

LP3991TL-1.5/NOPB from Texas Instruments is a fixed-output 1.5-V, 300-mA low-dropout (LDO) regulator in a 4-pin DSBGA package, designed for post-regulation after DC-DC converters in space-constrained digital systems. It operates from 1.65 V to 4 V input, delivers ±1% output accuracy at room temperature, maintains regulation down to 1.65 V input, and features 125-mV dropout at full 300-mA load.

For engineers reviewing the LP3991TL-1.5/NOPB datasheet, LP3991TL-1.5/NOPB pinout, LP3991TL-1.5/NOPB application, or LP3991TL-1.5/NOPB equivalent, key selection considerations include its ultra-low quiescent current (50 µA at 1 mA), 65 dB PSRR at 1 kHz, 280 µV_RMS output noise (10 Hz–100 kHz), stability with 0402 ceramic capacitors, and enable-controlled shutdown with 1.2-MΩ internal pulldown.

Technical Context

The LP3991TL-1.5/NOPB integrates a PMOS pass transistor enabling ultra-low dropout and high PSRR without requiring external compensation. Its EN pin accepts active-high logic control with 0.95 V threshold and includes an internal 1.2-MΩ pulldown resistor, allowing direct tie-to-VIN for always-on operation.

Designed specifically for low-voltage digital rails, it supports stable regulation across –40°C to +125°C junction temperature and remains functional with no-load conditions-critical for CMOS RAM keep-alive and battery-backed circuits. Output capacitor flexibility (4.7 µF for ≥1.5 V, 2.2 µF for <1.5 V) enables optimization of transient response versus board area.

Key Specifications

Pinout & Package

LP3991TL-1.5/NOPB uses a 4-pin DSBGA (YZR) package with 1.43 mm × 0.96 mm nominal body size and bottom-side solder bumps. The package is optimized for minimal PCB footprint and thermal conduction through the four terminals to the PCB.

Key Features

Applications

Equivalent & Alternatives

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

Compared with TPL7201515PDBVR and MCP1700T-1502E/TT, the LP3991TL-1.5/NOPB uniquely combines 300-mA capability, 125-mV dropout, DSBGA footprint, and 65 dB PSRR - making it the only option qualified for high-density, noise-sensitive, battery-powered digital core rails requiring precise 1.5-V regulation.

Availability

LP3991TL-1.5/NOPB is available at Aetrix Electronics and suitable for post-DC-DC regulation, battery-operated handhelds, and portable medical sensors requiring stable component supply, long-term lifecycle support, and traceable sourcing.

Supply support for LP3991TL-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

Texas Instruments is a global semiconductor leader specializing in analog, embedded processing, and power management technologies, with decades of LDO design expertise and broad automotive/industrial qualification.

The LP3991TL-1.5/NOPB belongs to TI's precision low-noise LDO family engineered for post-regulation in portable digital systems - emphasizing ultra-low dropout, ceramic-capacitor stability, and thermal robustness in miniature packages.

FAQ

What is the minimum input voltage required for LP3991TL-1.5/NOPB to maintain regulation?

The LP3991TL-1.5/NOPB maintains regulation down to 1.65 V input voltage - which is 150 mV above its 1.5-V output. This 150-mV headroom corresponds to its typical dropout specification at light loads; at 300 mA, dropout rises to 125 mV, meaning VIN ≥ 1.625 V is sufficient under full load. Operation below 1.65 V is not guaranteed per datasheet specifications.

Can LP3991TL-1.5/NOPB operate without an output load?

Yes, the LP3991TL-1.5/NOPB is explicitly specified to remain stable and in regulation with zero load current - a critical feature for CMOS RAM keep-alive, RTC backup, and other low-power standby applications. No minimum load or external bleed resistor is required, simplifying design and reducing power waste.

What output capacitor value is required for LP3991TL-1.5/NOPB?

For LP3991TL-1.5/NOPB (1.5-V output), a 4.7-µF ceramic capacitor (X7R or X5R dielectric, ESR 5–500 mΩ) is required. Capacitors must be rated for ≥6.3 V DC bias and placed within 1 cm of the OUT pin. While 2.2 µF may be used for outputs <1.5 V, it is not recommended for the 1.5-V variant due to measurable degradation in load transient response.

Does LP3991TL-1.5/NOPB require an input capacitor?

Yes, LP3991TL-1.5/NOPB requires a 1-µF ceramic capacitor connected between the IN pin and GND, placed ≤1 cm from the pin. This capacitor ensures stability and filters high-frequency noise from the input source. The datasheet permits increasing this value without limit, but does not specify ESR requirements - only capacitance tolerance and DC bias stability matter.

How is thermal performance managed in the LP3991TL-1.5/NOPB DSBGA package?

The LP3991TL-1.5/NOPB uses a 4-pin DSBGA (YZR) package with thermal conduction primarily through its four solder bumps into the PCB. Its junction-to-board thermal resistance (R_θJB) is 112.9°C/W, and junction-to-ambient (R_θJA) is 189.7°C/W on a high-K test board. Effective thermal management requires a solid copper pour connected to the GND bump (A1) and proper PCB stack-up - no external heatsink is needed for typical 300-mA operation.