Texas Instruments LP38843T-1.2/NOPB

Overview

LP38843T-1.2/NOPB from Texas Instruments is a 3A ultra-low-dropout linear regulator in TO-220 package, delivering fixed 1.2V output with 1.5% initial accuracy, 210mV typical dropout at 3A, and stable operation with ceramic output capacitors ≥22µF. It employs dual-input architecture (VIN for power, VBIAS for gate drive) and supports DSP/FPGA core supply and SMPS post-regulation in industrial embedded systems.

For engineers reviewing the LP38843T-1.2/NOPB datasheet, LP38843T-1.2/NOPB pinout, LP38843T-1.2/NOPB application, or LP38843T-1.2/NOPB equivalent, key selection factors include its 5-pin TO-220 thermal performance (θ_J-A = 65°C/W no heatsink), shutdown current of 30nA, load regulation of 0.1%/A, and bias voltage requirement of 4.5–5.5V.

Technical Context

The LP38843T-1.2/NOPB uses an N-MOS pass transistor driven by a separate VBIAS rail (4.5–5.5V), enabling ultra-low dropout operation even when VIN is only ~210mV above VOUT. Its CMOS-based control circuitry delivers 30mA typical quiescent current at full load and 30nA in shutdown, with internal overtemperature and overcurrent protection.

Stability is achieved with ≥22µF ceramic or ≥4.7µF tantalum output capacitance; input requires ≥10µF ceramic. PSRR reaches 80dB at 120Hz on VIN and 58dB on VBIAS, while output noise is 150µV_rms (10Hz–100kHz). The device operates across −40°C to +125°C junction temperature.

Key Specifications

Pinout & Package

LP38843T-1.2/NOPB is housed in a 5-lead TO-220 package (KC variant) with exposed tab electrically connected to GND. The tab serves as both thermal path and ground return, requiring direct PCB copper connection for optimal thermal performance and noise immunity.

Key Features

Applications

Equivalent & Alternatives

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

Compared with LP38843T-1.2/NOPB, TPS7A8300RGRT reduces system complexity by removing the VBIAS rail but sacrifices ultra-low-input capability; LT3080IDDPBF trades fixed-voltage precision and dropout performance for adjustability and higher current headroom.

Availability

LP38843T-1.2/NOPB is available at Aetrix Electronics and suitable for ASIC power supplies, SMPS post-regulation, DSP core rails, FPGA I/O domains, and server I/O voltage generation requiring stable component supply across industrial temperature ranges and long production lifecycles.

Supply support for LP38843T-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 linear regulation and thermal design.

The LP38843 series was designed specifically for high-current, low-noise post-regulation in computing and communications infrastructure, targeting applications demanding ultra-low dropout, ceramic-capacitor compatibility, and robust thermal behavior in TO-220 and DDPAK packages.

FAQ

What is the minimum output capacitance required for stable operation of LP38843T-1.2/NOPB?

The LP38843T-1.2/NOPB requires a minimum of 22µF ceramic (X7R or X5R dielectric) output capacitance placed within 1cm of the OUTPUT pin and returned to a clean analog ground. Tantalum capacitors may be used at 4.7µF minimum, but ceramic is preferred for lower ESR and better high-frequency noise suppression. Using Z5U or Y5V ceramics is prohibited due to severe capacitance loss over temperature and bias.

Can LP38843T-1.2/NOPB operate without an external VBIAS supply?

No - LP38843T-1.2/NOPB requires an external 4.5V to 5.5V VBIAS supply to drive the N-MOS pass transistor gate. This rail must be decoupled with a 0.1µF ceramic capacitor. If unused, the BIAS pin must still be connected to a valid 4.5–5.5V source; floating or grounding it will prevent regulation. The dual-rail architecture is fundamental to achieving 210mV dropout.

What is the thermal performance of LP38843T-1.2/NOPB in its TO-220 package?

In the TO-220 (KC) package, LP38843T-1.2/NOPB has a junction-to-ambient thermal resistance (θ_J-A) of 65°C/W with no heatsink. When mounted to a heatsink, θ_J-S drops to ~4°C/W. Maximum power dissipation without thermal shutdown depends on ambient temperature and heatsinking - e.g., at 25°C ambient and no heatsink, continuous dissipation is limited to ~1.5W to maintain ≤125°C junction temperature.

Does LP38843T-1.2/NOPB support reverse current protection?

No - LP38843T-1.2/NOPB does not integrate reverse current protection. If the output voltage exceeds the input (e.g., during hot-swap or backup power scenarios), current can flow backward from OUTPUT to IN. External protection (e.g., a Schottky diode in series with IN or an ideal diode controller) is required in such configurations to prevent damage or system instability.

How does the shutdown function behave on LP38843T-1.2/NOPB?

The SHUTDOWN (S/D) pin on LP38843T-1.2/NOPB is active-low. Pulling it below 0.7V turns off the output, reducing quiescent current to 30nA typical. It must be actively terminated with a pull-up resistor (10–100kΩ) to VBIAS if driven by an open-drain source. When tied to VBIAS, the device operates normally. Turn-off delay is 20µs; turn-on delay is 15µs under light load conditions.