Texas Instruments LP3961ES-3.3/NOPB

Overview

LP3961ES-3.3/NOPB from Texas Instruments is a fixed-output 3.3 V, 800-mA ultra-low-dropout linear regulator in SOT-223 package, featuring 24 mV dropout at 80 mA, ±1.5% output voltage accuracy, and an ERROR flag for output undervoltage detection - used in microprocessor core power supplies where tight regulation and fast load transient response are critical.

For engineers reviewing the LP3961ES-3.3/NOPB datasheet, LP3961ES-3.3/NOPB pinout, LP3961ES-3.3/NOPB application, or LP3961ES-3.3/NOPB equivalent, key selection considerations include dropout performance under 800-mA load, ERROR flag hysteresis behavior, thermal derating in SOT-223, ground current vs. load, and compatibility with low-ESR output capacitors (0.2–5 Ω).

Technical Context

The LP3961ES-3.3/NOPB uses a PMOS pass element with 240 mΩ typical R_DS(on), enabling ultra-low dropout operation down to 24 mV at light load and 240 mV at full 800-mA load. Its ERROR flag comparator monitors output voltage with 10% threshold and 5% hysteresis, asserting low when V_OUT falls below 2.97 V (for 3.3 V nominal), and features open-drain output requiring external pull-up.

It operates from 2.5 V to 7 V input, delivers ±1.5% initial output accuracy and ±3% over temperature (−40°C to 125°C), supports shutdown via CMOS-compatible SD pin with 1 nA leakage, and integrates overtemperature and short-circuit protection with 165°C thermal shutdown threshold and 2.8 A short-circuit current limit.

Key Specifications

Pinout & Package

SOT-223 (5-pin) package: 6.50 mm × 3.56 mm body, exposed thermal pad on bottom (pin 3), rated R_θJA = 65.2°C/W with standard 1-in² copper pour.

Key Features

Applications

Equivalent & Alternatives

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

Compared with TSS721AIPW, LP3961ES-3.3/NOPB delivers 60% higher current and real-time ERROR signaling; compared with TPS7A4701RGWR, it offers integrated fault flag and smaller SOT-223 footprint at the expense of 15 µV_RMS higher noise.

Availability

LP3961ES-3.3/NOPB is available at Aetrix Electronics and suitable for microprocessor core supplies, GTL+ bus terminators, SCSI termination circuits, and post-regulation of switching converters requiring stable component supply with guaranteed long-term sourcing.

Supply support for LP3961ES-3.3/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 connectivity technologies, with decades of LDO design heritage and broad industrial qualification.

The LP396x series was developed for high-current, low-dropout applications in microprocessor and bus-termination systems, emphasizing fast transient response, thermal robustness, and integrated fault signaling in compact packages.

FAQ

What is the minimum input voltage required for LP3961ES-3.3/NOPB to regulate 3.3 V at 800 mA?

The LP3961ES-3.3/NOPB requires a minimum input voltage of 3.54 V to maintain regulation at 800 mA, based on its 240 mV typical dropout voltage. At lower input voltages, output drops out of specification; the device remains functional down to 2.5 V input but cannot sustain 3.3 V output above ~100 mA below 3.54 V. Always verify margin using worst-case 350 mV dropout per datasheet.

How should the ERROR pin of LP3961ES-3.3/NOPB be connected in a system that does not monitor faults?

If the ERROR function is unused, the ERROR pin of LP3961ES-3.3/NOPB must be connected directly to GND per TI's datasheet guidance. Leaving it floating risks undefined logic states and potential noise coupling; pulling it high without a defined purpose wastes current and defeats the open-drain design intent. Grounding ensures predictable behavior and disables the flag safely.

Can LP3961ES-3.3/NOPB operate with a 10-µF ceramic output capacitor?

No - LP3961ES-3.3/NOPB requires a minimum 33 µF output capacitor with ESR between 0.2 Ω and 5 Ω for loop stability. A 10-µF ceramic capacitor typically has ESR <10 mΩ, which falls far below the 0.2 Ω lower bound and will cause oscillation. Use solid tantalum or polymer aluminum electrolytic capacitors meeting both capacitance and ESR specs, or parallel ceramics with resistive elements to raise effective ESR.

Does LP3961ES-3.3/NOPB support reverse current blocking when VOUT exceeds VIN?

LP3961ES-3.3/NOPB does not actively block reverse current; its internal PMOS pass transistor includes a parasitic body diode that conducts if VOUT rises above VIN. This diode tolerates up to 200 mA continuous or 1 A peak reverse current. For true reverse-current protection, an external Schottky diode or ideal diode controller must be added in series with the input or output path.

What is the thermal performance of LP3961ES-3.3/NOPB in SOT-223 on a standard 2-layer PCB?

On a standard 2-layer PCB with 1-in² copper pour connected to the exposed thermal pad, LP3961ES-3.3/NOPB has R_θJA = 65.2°C/W. At 800 mA and 3.54 V input (240 mV dropout), power dissipation is 192 mW; this yields ~12.5°C rise above ambient. Derate maximum current to ~650 mA at 70°C ambient to stay below 125°C junction limit - confirm with actual board layout and airflow conditions.