Texas Instruments LP38843T-1.5/NOPB

Overview

LP38843T-1.5/NOPB from Texas Instruments is a 3A ultra-low-dropout linear regulator with 1.5V fixed output, CMOS N-MOS pass transistor architecture, 210mV typical dropout at 3A, ±1.5% initial output accuracy, and stable operation with ceramic output capacitors. It delivers core power to DSPs and microcontrollers in space-constrained industrial and embedded systems where input-to-output voltage margin is minimal.

For engineers reviewing the LP38843T-1.5/NOPB datasheet, LP38843T-1.5/NOPB pinout, LP38843T-1.5/NOPB application, or LP38843T-1.5/NOPB equivalent, key selection criteria include dropout voltage at full load, bias rail dependency (4.5–5.5V VBIAS), thermal resistance (65°C/W, no heatsink), shutdown quiescent current (30nA), and TO-220 package mechanical compatibility.

Technical Context

The LP38843T-1.5/NOPB employs a dual-rail architecture: VIN supplies high-current load power while separate VBIAS (4.5–5.5V) drives the N-MOS gate, enabling operation with VIN as low as VOUT + 210mV. Its CMOS-based control circuitry achieves 30nA shutdown current and maintains stability with ≥22µF ceramic or ≥4.7µF tantalum output capacitance.

It integrates over-temperature and over-current protection, features 15µs turn-on delay and 20µs turn-off delay, and delivers 150µV_rms output noise (10Hz–100kHz) with PSRR of 80dB at 120Hz on VIN and 58dB on VBIAS - critical for noise-sensitive analog and mixed-signal loads.

Key Specifications

Pinout & Package

LP38843T-1.5/NOPB uses a 5-pin TO-220 (KC) package with exposed tab tied to GND. The tab serves as both thermal path and electrical ground connection, requiring direct PCB copper pour attachment for thermal management and noise control.

Key Features

Applications

Equivalent & Alternatives

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

Compared with TPS7A8300RGRT and LP38798SD-1.5/NOPB, the LP38843T-1.5/NOPB uniquely balances 3A capability, ultra-low dropout, and TO-220 mechanical compatibility - making it optimal for legacy industrial upgrades where heatsink mounting and through-hole assembly are required.

Availability

LP38843T-1.5/NOPB is available at Aetrix Electronics and suitable for ASIC power supplies in desktops and graphics cards, server core and I/O supplies, and DSP/FPGA power applications requiring stable component supply across long-lifecycle industrial programs.

Supply support for LP38843T-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 leader specializing in analog, embedded processing, and connectivity technologies, with decades of expertise in power management ICs.

The LP38843T-1.5/NOPB belongs to TI's ultra-low-dropout linear regulator product line, engineered for high-current, low-voltage core and I/O rail regulation in computing, communications, and industrial systems where efficiency, noise, and thermal performance are critical.

FAQ

What is the minimum input voltage required for stable operation of the LP38843T-1.5/NOPB?

The LP38843T-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 with tightly regulated intermediate rails such as 1.8V outputs from buck converters. Input must also meet recommended operating conditions: VIN ≥ (VOUT + VDO) and ≤5.5V, with VBIAS independently supplied at 4.5–5.5V.

Can the LP38843T-1.5/NOPB operate without an external bias voltage?

No - the LP38843T-1.5/NOPB requires an external 4.5–5.5V VBIAS supply to drive its N-MOS pass transistor gate and power internal circuitry. Without VBIAS, the device will not regulate, even if VIN is present. If bias is unavailable, tie the BIAS pin to a clean 5V rail; under-voltage lockout disables output if VBIAS falls below ~4V.

What output capacitor is required for stability with the LP38843T-1.5/NOPB?

The LP38843T-1.5/NOPB requires ≥22µF X7R or X5R ceramic output capacitance (or ≥4.7µF solid tantalum) placed within 1 cm of the OUTPUT pin and returned to clean analog ground. Z5U/Y5V ceramics are prohibited due to severe capacitance loss with temperature and bias voltage - using them risks instability and oscillation.

How does the shutdown function work on the LP38843T-1.5/NOPB?

The S/D pin is active-low: pulling it ≤0.3V turns off the output and reduces quiescent current to 30nA typical. For normal operation, tie S/D to VBIAS via a 10–100kΩ pull-up resistor. If driven by a CMOS rail-to-rail output, the pull-up may be omitted. Do not leave S/D floating - it must be actively terminated to ensure predictable enable/disable behavior.

Is a heatsink required for the LP38843T-1.5/NOPB in a 3A application?

A heatsink is required if power dissipation exceeds what the TO-220 package can handle at the target ambient temperature. With θ_J-A = 65°C/W (no heatsink), max allowable PD = (125°C − T_A) / 65. At T_A = 70°C, PD must stay ≤0.85W - corresponding to (VIN − 1.5V) × 3A ≤ 0.85W → VIN ≤ 1.78V. For higher VIN, a heatsink or PCB copper pour is mandatory to avoid thermal shutdown.