Texas Instruments LP38842T-1.5/NOPB

Overview

LP38842T-1.5/NOPB from Texas Instruments is a 1.5A ultra-low-dropout linear regulator with fixed 1.5V output, N-MOS pass transistor architecture, and dual-supply operation (VIN + VBIAS). It delivers 1.5% initial output accuracy, 115mV typical dropout at 1.5A, and stable regulation with ceramic output capacitors ≥22µF. It is used in FPGA core power supplies and SMPS post-regulation where input-to-output differential is constrained.

For engineers reviewing the LP38842T-1.5/NOPB datasheet, LP38842T-1.5/NOPB pinout, LP38842T-1.5/NOPB application, or LP38842T-1.5/NOPB equivalent, key selection criteria include bias rail dependency (4.5–5.5V), shutdown control via S/D pin, thermal derating in TO-220 package, and ceramic capacitor stability requirements.

Technical Context

The LP38842T-1.5/NOPB uses an N-MOS pass device driven by a separate VBIAS rail, enabling ultra-low dropout operation independent of VIN headroom-only VIN ≥ VOUT + VDO is required. Its CMOS-based control circuitry draws just 30mA quiescent current from VIN and 2mA from VBIAS at full load.

Stability is achieved using external ceramic output capacitance (≥22µF, X7R/X5R) and 10µF ceramic input capacitance; tantalum alternatives require only 4.7µF but sacrifice high-frequency noise suppression. The device integrates over-temperature and over-current protection, with thermal shutdown triggered above 150°C junction temperature.

Key Specifications

Pinout & Package

LP38842T-1.5/NOPB is housed in a 5-lead TO-220 (KC) package with exposed tab electrically connected to GND. The tab serves as primary thermal path and must be soldered to a copper plane or heatsink.

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 LT3080IM#PBF, LP38842T-1.5/NOPB uniquely supports sub-2V input operation via VBIAS separation, offers lowest dropout in its class, and guarantees ceramic-stable performance without ESR tuning-making it optimal for space-constrained, low-VIN FPGA/ASIC core rails.

Availability

LP38842T-1.5/NOPB is available at Aetrix Electronics and suitable for FPGA core supplies, server I/O rails, and SMPS post-regulation requiring stable component supply, long-lifecycle assurance, and TO-220 mechanical compatibility.

Supply support for LP38842T-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 power management ICs, with decades of LDO design heritage and automotive-grade reliability validation.

The LP38842 series was engineered for high-current, low-noise, ultra-low-dropout regulation in digital system power domains-including FPGA, ASIC, and processor core supplies-where traditional bipolar LDOs fail due to excessive dropout or quiescent current.

FAQ

What is the minimum input voltage required for LP38842T-1.5/NOPB to regulate 1.5V output?

The LP38842T-1.5/NOPB requires VIN ≥ VOUT + VDO. With 115mV typical dropout at 1.5A, the minimum functional VIN is 1.615V. However, recommended operating conditions specify VIN ≥ (VOUT + VDO) + margin-TI advises VIN ≥ VOUT + 1V for robust line regulation. So while 1.615V is technically viable under ideal conditions, 2.5V is preferred for full-spec operation across temperature and load.

Can LP38842T-1.5/NOPB operate without the VBIAS supply?

No. LP38842T-1.5/NOPB requires a 4.5–5.5V VBIAS supply to drive the gate of its N-MOS pass transistor. Omitting VBIAS prevents regulation entirely-the device will not produce 1.5V output regardless of VIN level. If no dedicated bias rail exists, TI recommends alternatives like TPS7A8300RGRT that integrate bias generation.

What ceramic capacitor dielectric types are approved for LP38842T-1.5/NOPB output stabilization?

Only X7R and X5R ceramic dielectrics are approved for the LP38842T-1.5/NOPB output capacitor. Z5U and Y5V types are explicitly prohibited because their capacitance degrades severely with temperature and DC bias-potentially falling below the 22µF minimum required for loop stability. X7R provides ±15% tolerance over −55°C to +125°C; X5R offers ±15% over −55°C to +85°C.

Does LP38842T-1.5/NOPB require a heatsink in TO-220 package at 1.5A load?

Yes-thermal analysis is mandatory. With θ_J-A = 65°C/W (no heatsink), 1.5A at 1.615V VIN yields ~165mW dissipation, raising junction temperature ~11°C above ambient. But at higher VIN (e.g., 3.3V), PD ≈ (3.3−1.5)V × 1.5A = 2.7W → ΔT ≈ 176°C. Since max T_J = 125°C, a heatsink is required whenever PD exceeds ~1.4W at 25°C ambient. Use TI's thermal calculator or Equation (3) from the datasheet to verify.

How does the shutdown (S/D) pin function on LP38842T-1.5/NOPB?

The S/D pin is active-low: pulling it ≤0.7V disables the output (shutdown current = 0.06µA typ); tying it to VBIAS (≥4.5V) enables regulation. It must be actively terminated-TI specifies a 10kΩ–100kΩ pull-up to VBIAS if driven by an open-drain source. Driving S/D directly from a CMOS output (rail-to-rail) eliminates the need for the pull-up resistor. Floating S/D is undefined and must be avoided.