Texas Instruments LP3855ESX-2.5/NOPB

Overview

LP3855ESX-2.5/NOPB from Texas Instruments is a fixed-output 2.5 V, 1.5 A ultra-low dropout linear regulator in SOT-223 package, featuring 24 mV dropout at 150 mA and 240 mV at 1.5 A, ±1.5% output voltage accuracy at 25°C, and remote-sense capability via dedicated SENSE pin for improved load regulation in distributed power systems.

For engineers reviewing the LP3855ESX-2.5/NOPB datasheet, LP3855ESX-2.5/NOPB pinout, LP3855ESX-2.5/NOPB application, or LP3855ESX-2.5/NOPB equivalent, key selection considerations include dropout performance under high load, ceramic capacitor stability support, shutdown control timing (25 µs turn-on delay), thermal derating in SOT-223 (R_θJA = 65.2°C/W), and remote-sense implementation for point-of-load accuracy.

Technical Context

The LP3855ESX-2.5/NOPB uses a CMOS-based PMOS pass transistor architecture enabling load-independent quiescent current (4 mA typical at 1.5 A) and ultra-low dropout operation. Its SENSE pin implements a Kelvin-sensing feedback path that regulates voltage directly at the remote load, decoupling trace resistance effects from output regulation.

It integrates overtemperature and overcurrent protection with thermal shutdown cycling behavior, supports stable operation with ≥10 µF ceramic or tantalum output capacitors, and features an open-drain SD input requiring external 10-kΩ pull-up for proper logic-level control - no internal hysteresis on shutdown threshold.

Key Specifications

Pinout & Package

SOT-223 (NDC) package: 6.50 mm × 3.56 mm body, thermally enhanced with exposed pad (not electrically connected); 5-pin configuration optimized for PCB heat dissipation in space-constrained layouts.

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 TPS7A4701RGWR, the LP3855ESX-2.5/NOPB uniquely delivers 1.5 A current, SENSE-based remote regulation, and sub-250 mV dropout in a thermally efficient SOT-223 package - making it optimal for high-current, point-of-load applications where trace resistance and thermal constraints dominate.

Availability

LP3855ESX-2.5/NOPB is available at Aetrix Electronics and suitable for microprocessor core supplies, GTL bus terminators, post-regulators for switching supplies, battery-powered instrumentation, and high-efficiency linear regulator designs requiring stable component supply across production lifecycles.

Supply support for LP3855ESX-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 leader specializing in analog, embedded processing, and power management technologies, with decades of expertise in precision linear regulation and high-reliability power solutions.

The LP3855ESX-2.5/NOPB belongs to TI's LP385x ultra-low dropout regulator family, designed specifically for fast-transient, low-voltage digital systems including microprocessors, FPGAs, and memory interfaces where remote sensing and minimal dropout are critical.

FAQ

What is the minimum input voltage required for LP3855ESX-2.5/NOPB to regulate 2.5 V output?

The LP3855ESX-2.5/NOPB requires input voltage ≥ V_OUT(NOM) + V_DROPOUT. At 1.5 A load and 25°C, dropout is 240 mV, so minimum input is 2.74 V. Per datasheet Section 8.3, absolute minimum operating VIN is 2.5 V - but regulation is only guaranteed above V_OUT + V_DROPOUT. Below that, output sags proportionally.

Can LP3855ESX-2.5/NOPB operate with only ceramic capacitors, and what are the limits?

Yes - LP3855ESX-2.5/NOPB is stable with ceramic output capacitors. With 10 µF ceramic input capacitance and 1.5 A load, maximum stable ceramic output capacitance is ~150 µF (per Figure 21). Total ceramic C_OUT must include all bypass caps on the same net. Minimum remains 10 µF for loop stability across all conditions.

How should the SENSE pin be connected if remote sensing is not needed for LP3855ESX-2.5/NOPB?

If remote sensing is unused, the SENSE pin must be connected directly to the OUT pin - not to GND or left floating. This configures LP3855ESX-2.5/NOPB to regulate at the device output terminal, matching standard LDO behavior. Leaving SENSE unconnected risks instability or undefined regulation.

What is the shutdown behavior of LP3855ESX-2.5/NOPB, and how is SD pin biased?

The SD pin is active-low. Pulling SD ≤ 0.3 V turns off LP3855ESX-2.5/NOPB; rising threshold is 1.3–2.0 V. A 10-kΩ pull-up resistor to VIN is mandatory unless driven by a rail-to-rail CMOS output. During shutdown, ground current drops to ≤10 µA and ERROR pin becomes invalid - confirming low-power state.

Does LP3855ESX-2.5/NOPB include reverse current protection, and what are its limits?

LP3855ESX-2.5/NOPB contains an inherent PMOS body diode between IN and OUT. If V_OUT > V_IN, reverse current flows through this diode. It is rated for 200 mA DC and 1 A peak - exceeding this risks latch-up or thermal failure. External reverse-blocking MOSFETs are recommended in back-drive scenarios.