Texas Instruments LP38843SX-1.5/NOPB

Overview

LP38843SX-1.5/NOPB from Texas Instruments is a 3A ultra-low-dropout linear regulator with fixed 1.5V output, CMOS N-MOS pass transistor architecture, 210mV dropout at 3A, ±1.5% initial output accuracy, and stable operation with ceramic output capacitors ≥22µF. It is used in FPGA core power supplies, DSP post-regulation, and server I/O rails where tight voltage tolerance and fast transient response are critical.

For engineers reviewing the LP38843SX-1.5/NOPB datasheet, LP38843SX-1.5/NOPB pinout, LP38843SX-1.5/NOPB application, or LP38843SX-1.5/NOPB equivalent, key selection criteria include bias rail dependency (4.5–5.5V), thermal resistance of 35°C/W (DDPAK/TO-263 on 1-in² copper), shutdown threshold (0.3–0.7V), and compatibility with low-ESR ceramic capacitors only.

Technical Context

The LP38843SX-1.5/NOPB employs a dual-rail architecture: VIN supplies load current while VBIAS (4.5–5.5V) powers internal circuitry and drives the N-MOS gate, enabling operation with input as low as VOUT + 210mV. Its CMOS design delivers 30nA shutdown current and maintains stability without requiring high-ESR tantalum capacitors.

It features over-temperature and over-current protection, 150µV_rms output noise (10Hz–100kHz), and 80dB PSRR at 120Hz on VIN. The device operates across −40°C to +125°C junction temperature and requires no external compensation when paired with ≥22µF X7R/X5R ceramic output capacitance.

Key Specifications

Pinout & Package

LP38843SX-1.5/NOPB uses the DDPAK/TO-263 (KTT) 5-pin package with exposed thermal pad soldered to PCB copper plane for heatsinking. Pin 1 (INPUT) and Pin 5 (SHUTDOWN) are on one side; Pin 2 (BIAS), Pin 3 (GND), and Pin 4 (OUTPUT) occupy the opposite edge. The metal tab is electrically connected to GND.

Key Features

Applications

Equivalent & Alternatives

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

Compared with TPS7A8300RGRT and LP3985IM5-1.5/NOPB, the LP38843SX-1.5/NOPB uniquely supports 3A loads with ultra-low dropout and dual-rail flexibility, making it irreplaceable in high-current, low-VIN FPGA and server I/O applications where bias rail availability is acceptable.

Availability

LP38843SX-1.5/NOPB is available at Aetrix Electronics and suitable for FPGA core power supplies, DSP post-regulators, and server I/O voltage rails requiring stable component supply, long-term lifecycle assurance, and RoHS-exempt manufacturing compliance.

Supply support for LP38843SX-1.5/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, specializing in analog ICs, embedded processors, and high-reliability power management solutions for industrial, automotive, and communications markets.

The LP38843 family was designed specifically for high-current, ultra-low-dropout regulation in digital system power rails-targeting FPGA, ASIC, and DSP core supplies where ceramic capacitor compatibility and thermal efficiency are essential.

FAQ

What is the minimum input voltage required for LP38843SX-1.5/NOPB to regulate 1.5V at 3A?

The LP38843SX-1.5/NOPB requires a minimum input voltage of VOUT + VDO = 1.5V + 0.21V = 1.71V at 3A load. This ultra-low dropout enables use after low-headroom DC-DC converters. Input must also meet recommended operating condition VIN ≥ (VOUT + VDO), and VBIAS must be independently supplied at 4.5–5.5V.

Can LP38843SX-1.5/NOPB operate without a separate VBIAS supply?

No. LP38843SX-1.5/NOPB requires an external 4.5–5.5V VBIAS rail to power internal circuitry and drive the N-MOS gate. Omitting VBIAS prevents regulation-even if VIN is present-because the pass transistor cannot be enabled. If no dedicated bias rail exists, a local LDO or resistor-divider + LDO from VIN is necessary.

What output capacitor value and type are mandatory for stable operation of LP38843SX-1.5/NOPB?

LP38843SX-1.5/NOPB requires ≥22µF X7R or X5R ceramic output capacitance placed ≤1 cm from the OUTPUT pin with low-inductance ground return. Tantalum capacitors are not recommended; Z5U/Y5V ceramics are prohibited due to severe capacitance loss with voltage/temperature. Using <22µF ceramic causes instability and oscillation.

How does the thermal performance of LP38843SX-1.5/NOPB compare between TO-220 and DDPAK/TO-263 packages?

LP38843SX-1.5/NOPB in DDPAK/TO-263 (KTT) achieves θ_J-A = 35°C/W when soldered to ≥1-in² copper, versus 65°C/W for TO-220 without heatsink. This 46% lower thermal resistance allows 3A operation at higher ambient temperatures or reduced PCB heatsinking area-critical for dense server and graphics card layouts.

Does LP38843SX-1.5/NOPB include reverse polarity or reverse current protection?

No. LP38843SX-1.5/NOPB lacks reverse polarity or reverse current protection. If the output voltage exceeds the input (e.g., during hot-swap or backup battery scenarios), current can flow backward through the N-MOS pass transistor. An external Schottky diode in series with INPUT is required for reverse-current blocking in such applications.