Texas Instruments LP3961ESX-2.5/NOPB

Overview

LP3961ESX-2.5/NOPB from Texas Instruments is a fixed-output 2.5 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 integrated ERROR flag for output monitoring - used in microprocessor core power supplies where tight regulation and fast load transient response are critical.

For engineers reviewing the LP3961ESX-2.5/NOPB datasheet, LP3961ESX-2.5/NOPB pinout, LP3961ESX-2.5/NOPB application, or LP3961ESX-2.5/NOPB equivalent, key selection considerations include dropout performance under 800-mA load, ERROR flag hysteresis behavior, thermal shutdown threshold (165°C), ground current vs. load dependency, and compatibility with low-ESR output capacitors (0.2–5 Ω).

Technical Context

The LP3961ESX-2.5/NOPB employs a PMOS pass transistor architecture enabling ultra-low dropout operation independent of load current, with typical R_DS(on) of 240 mΩ. Its ERROR flag uses an open-drain comparator with 10% output voltage threshold and 5% hysteresis, active only when the device is not in shutdown mode.

It operates across −40°C to 125°C junction temperature, supports input voltages from 2.5 V to 7 V, and delivers stable 2.5 V output with 0.02% load regulation and 15 µA shutdown quiescent current. The internal thermal shutdown circuit activates at 165°C with 10°C hysteresis.

Key Specifications

Pinout & Package

SOT-223 (5-pin) package: 6.50 mm × 3.56 mm body size, thermally enhanced with exposed pad (pin 5 = GND). Designed for surface-mount assembly and moderate-power dissipation with PCB copper pour.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar ultra-low-dropout linear regulator applications.

Compared with TSS721AIDR and TPS7A2025PDQNR, the LP3961ESX-2.5/NOPB uniquely combines 800 mA capability, 24 mV ultra-low dropout, and integrated ERROR flag in SOT-223 - making it the only option among the three suitable for 2.5 V microprocessor core supplies requiring both high current and fault reporting.

Availability

LP3961ESX-2.5/NOPB is available at Aetrix Electronics and suitable for microprocessor core supplies, GTL+ bus terminators, post-regulation of switching converters, and SCSI termination circuits requiring stable component supply, long-term lifecycle support, and traceable sourcing.

Supply support for LP3961ESX-2.5/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 company headquartered in Dallas, Texas, designing and manufacturing analog and embedded processing chips for industrial, automotive, and communications markets.

The LP396x series was developed specifically for high-efficiency, low-noise linear regulation in low-voltage digital systems - targeting applications demanding ultra-low dropout, fast transient response, and integrated fault monitoring without external components.

FAQ

What is the minimum input voltage required for LP3961ESX-2.5/NOPB to regulate 2.5 V output?

The LP3961ESX-2.5/NOPB requires a minimum input voltage of 2.5 V plus dropout voltage. At 800 mA load, dropout is 240 mV, so minimum VIN is 2.74 V. However, per datasheet Section 6.3, the absolute minimum operating VIN is specified as 2.5 V - meaning it can sustain regulation down to 2.5 V only at very light loads where dropout approaches zero. For full 800 mA operation, VIN ≥ 2.74 V is required. The LP3961ESX-2.5/NOPB will not maintain regulation if VIN falls below this margin.

How does the ERROR flag on LP3961ESX-2.5/NOPB behave during shutdown?

The ERROR flag on LP3961ESX-2.5/NOPB is disabled and invalid when the SD pin is pulled low - the internal comparator is powered down to minimize leakage. During shutdown, the ERROR pin floats high-impedance unless externally pulled. It resumes active monitoring only after SD returns high and the regulator re-establishes regulation. This behavior is explicitly documented in Section 7.3.2 of the SNVS056J datasheet. The LP3961ESX-2.5/NOPB ERROR pin must never be left floating in active mode; a 10-kΩ pullup to IN is mandatory.

Can LP3961ESX-2.5/NOPB operate with ceramic output capacitors?

No - the LP3961ESX-2.5/NOPB requires an output capacitor with ESR between 0.2 Ω and 5 Ω for loop stability, and standard ceramic capacitors have ESR far below 0.2 Ω (typically <10 mΩ), causing instability and oscillation. The datasheet explicitly states ceramics are unsuitable for the output (Section 8.2.2.1.2). Acceptable alternatives include solid tantalum or polymer aluminum capacitors meeting the ESR range. The LP3961ESX-2.5/NOPB can use ceramic capacitors on the input side, however.

What thermal derating applies to LP3961ESX-2.5/NOPB in SOT-223 package at 85°C ambient?

In SOT-223 (NDC package), the LP3961ESX-2.5/NOPB has R_θJA = 65.2°C/W. At 85°C ambient and maximum junction temperature of 125°C, allowable power dissipation is (125 − 85)/65.2 ≈ 0.613 W. With 2.5 V output and 800 mA load, power dissipated is (VIN − 2.5) × 0.8. Solving for VIN gives ~3.26 V maximum for safe operation. Higher input voltages require reduced load current or enhanced PCB copper to lower effective R_θJA. The LP3961ESX-2.5/NOPB thermal shutdown activates at 165°C, providing final safety margin.

Does LP3961ESX-2.5/NOPB support reverse current protection?

Yes - the LP3961ESX-2.5/NOPB contains an internal PMOS pass transistor with an inherent body diode. When the output voltage exceeds the input (e.g., during hot-swap or backup power scenarios), this diode becomes forward-biased. The device tolerates up to 200 mA continuous and 1 A peak reverse current, as stated in Section 6.1 Absolute Maximum Ratings. This feature prevents damage to upstream sources and avoids uncontrolled discharge paths. The LP3961ESX-2.5/NOPB does not actively block reverse current but limits its magnitude within safe bounds.