Texas Instruments LP3855EMP-5.0/NOPB

Overview

LP3855EMP-5.0/NOPB from Texas Instruments is a fixed-output 5.0 V, 1.5 A ultra-low dropout linear regulator in SOT-223 package, featuring 240 mV dropout at full load, ±1.5% output voltage accuracy at 25°C, and remote sense (SENSE) capability for improved load regulation in distributed power systems.

For engineers reviewing the LP3855EMP-5.0/NOPB datasheet, LP3855EMP-5.0/NOPB pinout, LP3855EMP-5.0/NOPB application, or LP3855EMP-5.0/NOPB equivalent, key selection considerations include dropout performance under 1.5 A load, SENSE pin implementation for remote load regulation, shutdown control timing (25 µs turn-on delay), thermal derating in SOT-223 (R_θJA = 65.2°C/W), and ceramic capacitor stability compliance.

Technical Context

The LP3855EMP-5.0/NOPB uses a CMOS-based PMOS pass transistor architecture enabling load-independent quiescent current (4 mA typical at 1.5 A), ultra-low dropout (24 mV at 150 mA; 240 mV at 1.5 A), and fast transient response to step-load changes-critical for microprocessor core supply rails. Its SENSE pin provides feedback directly at the load point, decoupling regulation from PCB trace IR drop.

It operates across 2.5 V to 7 V input range with integrated overtemperature and overcurrent protection, shutdown functionality (10 nA quiescent in SD mode), and open-drain ERROR flag logic (not present on LP3855; only LP3852 has ERROR). The SOT-223 package requires no external heat sink below ~0.8 W dissipation at 25°C ambient.

Key Specifications

Pinout & Package

SOT-223 (NDC) package: 5-pin surface-mount, 6.50 mm × 3.56 mm body, exposed thermal pad (pin 4 is GND-connected tab).

Key Features

Applications

Equivalent & Alternatives

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

Compared with TSS721AIDR, LP3855EMP-5.0/NOPB delivers superior remote load regulation and lower thermal resistance in SOT-223; versus TPS7A4700RGWR, it trades adjustability and ultra-low noise for higher current and dedicated SENSE functionality essential in distributed digital power architectures.

Availability

LP3855EMP-5.0/NOPB is available at Aetrix Electronics and suitable for microprocessor core supplies, GTL bus terminators, SCSI active terminators, and battery-powered instrumentation requiring stable component supply with guaranteed long-term sourcing.

Supply support for LP3855EMP-5.0/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 specializing in analog and embedded processing solutions, with leadership in power management ICs since the 1980s.

The LP3855EMP-5.0/NOPB belongs to TI's LP385x family of ultra-low dropout regulators, designed specifically for high-current, low-voltage microprocessor and digital logic applications demanding fast transient response and remote load regulation.

FAQ

What is the minimum input voltage required for LP3855EMP-5.0/NOPB to maintain regulation?

The LP3855EMP-5.0/NOPB requires VIN ≥ VOUT + V_DROPOUT. At 1.5 A load, dropout is 240 mV, so minimum input is 5.24 V. At lighter loads (e.g., 150 mA), dropout drops to 24 mV, allowing VIN as low as 5.024 V. The absolute minimum operating VIN is 2.5 V, but that only applies for output voltages ≤2.5 V - not relevant for the 5.0 V LP3855EMP-5.0/NOPB.

Can LP3855EMP-5.0/NOPB be used with ceramic output capacitors, and what are the stability limits?

Yes, LP3855EMP-5.0/NOPB is certified stable with ceramic output capacitors ≥10 µF. For 1.5 A load and 10 µF ceramic input capacitance, maximum stable ceramic output capacitance is ~150 µF. Exceeding this risks oscillation; always verify stability with actual layout parasitics. Ceramic caps reduce ESR-related losses and improve high-frequency transient response versus tantalum.

How should the SENSE pin be connected in LP3855EMP-5.0/NOPB if remote load regulation is not needed?

If remote sensing is not required, the SENSE pin of LP3855EMP-5.0/NOPB must be connected directly to the OUT pin - not left floating or tied to GND. This configuration configures the device to regulate at the OUT pin, matching standard LDO behavior. Leaving SENSE unconnected violates bias conditions and may cause regulation failure or instability.

Does LP3855EMP-5.0/NOPB include an ERROR flag output like the LP3852?

No, LP3855EMP-5.0/NOPB does not have an ERROR pin. That function is exclusive to the LP3852 variant. The LP3855 family replaces ERROR with the SENSE pin for remote voltage feedback. If fault monitoring is required, external circuitry (e.g., voltage supervisor on VOUT) must be added - the LP3855EMP-5.0/NOPB itself provides no built-in output status flag.

What thermal derating applies to LP3855EMP-5.0/NOPB in SOT-223 package at 60°C ambient?

With R_θJA = 65.2°C/W and max T_J = 125°C, the allowable temperature rise is 65°C. At 60°C ambient, max allowable ΔT is 65°C, so max power dissipation is 65°C ÷ 65.2°C/W ≈ 0.997 W. At 5.0 V output, this limits usable output current to ~0.997 W ÷ (5.0 V – V_{IN_MIN}) - e.g., with VIN = 5.5 V, max I_OUT ≈ 1.99 A, but practical limit remains 1.5 A due to internal current limit and safe operating area.