Texas Instruments LP3855EMP-2.5/NOPB

Overview

LP3855EMP-2.5/NOPB from Texas Instruments is a fixed-output 2.5 V, 1.5 A ultra-low dropout linear regulator in TO-220-5 package, featuring SENSE pin for remote load regulation, 240 mV dropout at 1.5 A, ±1.5% output voltage accuracy at 25°C, and integrated overtemperature/overcurrent protection - used in microprocessor core supplies and post-regulation of switching converters.

For engineers reviewing the LP3855EMP-2.5/NOPB datasheet, LP3855EMP-2.5/NOPB pinout, LP3855EMP-2.5/NOPB application, or LP3855EMP-2.5/NOPB equivalent, key selection considerations include remote-sense capability, ceramic-capacitor stability support, shutdown control timing (25 µs turn-on), thermal derating in TO-220 (R_θJA = 32°C/W), and dropout performance across –40°C to 125°C junction temperature.

Technical Context

The LP3855EMP-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 - 24 mV at 150 mA and 240 mV at 1.5 A. Its SENSE pin implements Kelvin sensing to regulate voltage directly at the remote load, compensating for PCB trace resistance up to ~100 mΩ.

It operates from 2.5 V to 7 V input, supports stable operation with ≥10 µF ceramic or tantalum output capacitance, and includes active-low shutdown (1.3–2.0 V threshold), open-drain ERROR flag (not present on LP3855), and internal short-circuit/thermal foldback protection - all specified across –40°C to 125°C junction temperature.

Key Specifications

Pinout & Package

LP3855EMP-2.5/NOPB uses the TO-220-5 (NDH) package: 14.986 mm × 10.16 mm body, vertical leads, exposed tab for thermal conduction. Pin 1 = SD (shutdown input), Pin 2 = IN (input supply), Pin 3 = GND (ground), Pin 4 = OUT (regulated output), Pin 5 = SENSE (remote sense input).

Key Features

Applications

Equivalent & Alternatives

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

Compared with LP3852EMP-2.5/NOPB, the LP3855EMP-2.5/NOPB trades ERROR flag functionality for SENSE-based regulation - improving load accuracy at remote nodes but removing output fault indication. Versus TSS721AIPW, it delivers superior noise rejection and lower dropout, but omits current-sense capability.

Availability

LP3855EMP-2.5/NOPB is available at Aetrix Electronics and suitable for microprocessor core supplies, GTL bus terminators, and battery-powered instrumentation requiring stable component supply, long-lifecycle availability, and industrial-grade temperature performance.

Supply support for LP3855EMP-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, embedded processing, and logic ICs for industrial, automotive, and communications markets.

The LP3855EMP-2.5/NOPB belongs to TI's LP385x ultra-low dropout linear regulator family, engineered specifically for high-current, low-voltage applications demanding fast transient response, ceramic-capacitor compatibility, and remote load regulation - targeting FPGA, DSP, and microprocessor power delivery.

FAQ

What is the minimum input voltage required for LP3855EMP-2.5/NOPB to maintain regulation at full 1.5 A load?

The LP3855EMP-2.5/NOPB requires a minimum input voltage of 2.74 V to sustain 2.5 V output at 1.5 A, based on its 240 mV dropout specification. This value is derived from V_IN(MIN) = V_OUT + V_DROPOUT = 2.5 V + 0.24 V. Operation below this voltage results in unregulated output, and the device may enter dropout or thermal shutdown depending on ambient conditions and heatsinking.

Can LP3855EMP-2.5/NOPB operate with only ceramic capacitors, and what are the stability limits?

Yes, LP3855EMP-2.5/NOPB is stable with ceramic output capacitors ranging from 10 µF to 150 µF when paired with a 10 µF ceramic input capacitor at 1.5 A load - per Figure 21 in the SNVS174I datasheet. Exceeding 150 µF output capacitance risks instability unless input capacitance is increased proportionally. The regulator does not require ESR, unlike older LDOs, making it compatible with low-ESR MLCCs.

How should the SENSE pin be connected if remote sensing is not needed for LP3855EMP-2.5/NOPB?

If remote sensing is not required, the SENSE pin of LP3855EMP-2.5/NOPB must be connected directly to the OUT pin using a short, low-impedance trace - as explicitly stated in Section 10.1 of the datasheet. Leaving SENSE floating will cause regulation failure. This configuration reverts the device to standard local regulation mode while preserving all other LP3855EMP-2.5/NOPB specifications.

What thermal derating applies to LP3855EMP-2.5/NOPB in TO-220 package without a heatsink?

Without a heatsink, LP3855EMP-2.5/NOPB in TO-220 (NDH) has R_θJA = 32°C/W. At 1.5 A load with 2.74 V input, power dissipation is (2.74 V − 2.5 V) × 1.5 A ≈ 0.36 W. This yields ~11.5°C rise above ambient - well within the 125°C max junction limit at ≤113°C ambient. Derating becomes necessary only above ~100°C ambient or with higher input voltages.

Does LP3855EMP-2.5/NOPB include reverse current protection, and how is it implemented?

LP3855EMP-2.5/NOPB does not include active reverse current protection, but its internal PMOS pass transistor contains a parasitic body diode that conducts if V_OUT > V_IN. The datasheet specifies this diode can safely handle 200 mA continuous and 1 A peak reverse current. To prevent unintended backfeed, external Schottky diodes or ideal diode controllers are recommended in bidirectional or hot-swap applications.