Texas Instruments LP38855S-1.2/NOPB

Overview

LP38855S-1.2/NOPB from Texas Instruments is a 1.5A fast-response, high-accuracy LDO linear regulator with dual-rail operation (VIN and VBIAS), delivering a fixed 1.2V output with ±1.0% tolerance at 25°C, 130 mV typical dropout at 1.5A, and stable operation using only 10 µF ceramic output capacitance. It serves as a core voltage regulator for DSPs, FPGAs, and SMPS post-regulation in server and graphics card power systems.

For engineers reviewing the LP38855S-1.2/NOPB datasheet, LP38855S-1.2/NOPB pinout, LP38855S-1.2/NOPB application, or LP38855S-1.2/NOPB equivalent, key selection considerations include its dual-supply architecture (VIN/VBIAS), ultra-low ground current (12 mA at 1.5A), 1 µA shutdown current, thermal shutdown (160°C), and compatibility with low-ESR ceramic capacitors without external compensation.

Technical Context

The LP38855S-1.2/NOPB employs an N-MOS pass transistor driven by a separate VBIAS rail (3.0–5.5V), enabling ultra-low VIN operation down to VOUT + VDO while maintaining fast transient response and wide bandwidth. Its CMOS-based control circuitry delivers low quiescent current across load range and integrates under-voltage lockout (UVLO) with 2.45V threshold and 150 mV hysteresis.

It features internal enable logic with 1.25V turn-on threshold (100 mV hysteresis), thermal shutdown with 10°C hysteresis, over-current protection, and stability with minimal external components: 10 µF ceramic on OUT, 10 µF on IN, and 1 µF on BIAS - all specified per JEDEC standards for industrial temperature range (−40°C to +125°C).

Key Specifications

Pinout & Package

LP38855S-1.2/NOPB uses the DDPAK/TO-263 (KTT0005B) 5-lead surface-mount package with exposed thermal tab soldered to PCB copper plane for enhanced thermal performance (θJC = 3°C/W, θJA = 32°C/W min with 1-in² copper).

Key Features

Applications

Equivalent & Alternatives

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

Compared with TPS7A8300RGRT, LP38855S-1.2/NOPB offers lower dropout (130 mV vs. 200 mV), better PSRR (80 dB vs. 60 dB @ 120 Hz), and dual-rail flexibility - making it superior for high-efficiency, low-noise, and low-input-voltage applications where bias rail isolation is available.

Availability

LP38855S-1.2/NOPB is available at Aetrix Electronics and suitable for server core supplies, FPGA configuration rails, graphics card memory regulation, and industrial embedded power systems requiring stable component supply across extended temperature and long production lifecycles.

Supply support for LP38855S-1.2/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 ICs, with decades of expertise in high-reliability power solutions for industrial and computing markets.

The LP38855 series was designed specifically for high-current, low-dropout regulation in advanced digital systems - targeting DSP, FPGA, and ASIC core supplies where fast transient response, tight voltage tolerance, and dual-rail flexibility are mandatory.

FAQ

What is the minimum input voltage required for LP38855S-1.2/NOPB to regulate 1.2V output?

The minimum VIN is defined by the dropout voltage: VIN ≥ VOUT + VDO. For LP38855S-1.2/NOPB, VDO is 130 mV typical at 1.5A, so VIN must be ≥ 1.33V under full load. At lighter loads, VDO decreases - e.g., ~50 mV at 100 mA - allowing VIN as low as 1.25V while maintaining regulation. Note that VIN must also remain ≤ VBIAS (3.0–5.5V) per operating ratings.

Can LP38855S-1.2/NOPB operate without a VBIAS supply?

No. LP38855S-1.2/NOPB requires a valid VBIAS supply between 3.0V and 5.5V to power its internal reference, error amplifier, and gate driver. If VBIAS falls below the UVLO threshold (~2.45V), the device disables regardless of EN state or VIN level. The VBIAS rail is mandatory - it cannot be omitted or tied to VIN.

What ceramic capacitor dielectric types are approved for LP38855S-1.2/NOPB output stabilization?

Only X5R and X7R dielectrics are approved for the 10 µF output capacitor per TI's design guidelines. Z5U and Y5F types are explicitly excluded due to insufficient capacitance retention over temperature. The capacitor must be placed within 1 cm of the OUT pin and returned directly to the GND pin - not to a distant ground plane - to ensure loop stability and transient performance.

Does LP38855S-1.2/NOPB support reverse voltage protection?

Yes - inherently. The NMOS pass transistor has no parasitic body diode, so reverse current from OUT to IN is blocked when the gate is un-driven (i.e., during UVLO or EN = low). However, if VBIAS > UVLO and EN is active while VIN collapses, the controller drives the gate fully, enabling reverse conduction limited only by RDS(ON). Thus, reverse voltage protection is conditional and requires proper sequencing or external clamping for sustained reverse conditions.

How does the thermal performance of LP38855S-1.2/NOPB compare between TO-220 and DDPAK packages?

Both LP38855T-1.2/NOPB (TO-220) and LP38855S-1.2/NOPB (DDPAK/TO-263) share identical θJC = 3°C/W, but differ in θJA: TO-220 is 60°C/W with no heatsink, while DDPAK achieves 32°C/W minimum when soldered to 1-in² 1-oz copper. This gives LP38855S-1.2/NOPB up to 2× higher power dissipation capability in PCB-limited thermal environments - critical for compact, fanless server modules.