Diodes Incorporated AP1084TL-U

Overview

AP1084TL-U from Diodes Incorporated is a 5A low-dropout positive adjustable or fixed-mode linear regulator in TO220-3L package, featuring 1.4V maximum dropout at full load, ±1.5% output voltage accuracy (3.3V fixed version), and built-in thermal shutdown. It delivers stable 3.3V/5A output from 4.8–12V input for high-speed bus termination and VGA card power rails.

For engineers reviewing the AP1084TL-U datasheet, AP1084TL-U pinout, AP1084TL-U application, or AP1084TL-U equivalent, key selection criteria include dropout voltage under 5A load, thermal resistance (θ_JA = 78°C/W), minimum 10µF output capacitance requirement, and fixed 3.3V output configuration with adjustable mode disabled via internal GND connection.

Technical Context

The AP1084TL-U operates as a three-terminal LDO regulator with internal 1.25V reference and current-limited pass transistor. Its feedback loop uses an external resistor divider only in adjustable mode; the TL-U variant is factory-configured for 3.3V fixed output, tying the Adj pin internally to GND.

It employs thermal shutdown activation at 150°C junction temperature and incorporates current limiting at 5.1A. Stability relies on ≥10µF output capacitor with ESR between 0.15Ω and 20Ω, and regulation requires VIN ≥ VOUT + 1.4V across the full 0–5A load range.

Key Specifications

Pinout & Package

AP1084TL-U uses TO220-3L package with exposed thermal tab electrically connected to VOUT pin. The tab must be mounted to a heatsink or copper pour for thermal management. Pin 1 is Adj (GND for fixed mode), Pin 2 is VOUT (tab-connected), Pin 3 is VIN.

Key Features

Applications

Equivalent & Alternatives

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

Compared with AP1084K33L-13, the AP1084TL-U trades thermal efficiency for through-hole mounting flexibility; versus LM1084IT-3.3/NOPB, it offers tighter output tolerance and lower dropout, improving efficiency in margin-constrained 5V-input systems.

Availability

AP1084TL-U is available at Aetrix Electronics and suitable for PCI Express bus termination, VGA graphics card power delivery, and industrial PLC I/O modules requiring stable component supply with long lifecycle support.

Supply support for AP1084TL-U 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

Diodes Incorporated is a global manufacturer of discrete semiconductors and analog ICs, headquartered in Plano, Texas, with design and manufacturing operations across Asia and the Americas.

The AP1084 belongs to Diodes' high-current LDO regulator product line, engineered specifically for low-voltage, high-current point-of-load applications in computing, graphics, and industrial control systems.

FAQ

What is the minimum input voltage required for AP1084TL-U to regulate 3.3V at 5A?

The AP1084TL-U requires VIN ≥ VOUT + 1.4V to maintain regulation at full load, so minimum input is 4.7V. At lower inputs, output voltage drops linearly with VIN - e.g., at 4.5V input, output falls to ~3.1V. This 1.4V dropout is guaranteed across temperature and process variation per datasheet Rev. 9, page 5.

Can AP1084TL-U be used in adjustable mode despite its fixed 3.3V marking?

No. The TL-U suffix denotes factory-trimmed fixed 3.3V output with the Adj pin internally connected to GND. External resistor networks cannot override this configuration. For adjustable operation, select AP1084TL-U's adjustable counterpart, such as AP1084TL-ADJ, which leaves the Adj pin accessible and uncommitted.

What output capacitor is mandatory for stability with AP1084TL-U?

A minimum 10µF aluminum or tantalum capacitor with ESR between 0.15Ω and 20Ω is required from VOUT to GND. Ceramic capacitors alone are insufficient due to ultra-low ESR causing phase-margin loss. Diodes recommends 100µF/16V electrolytic (e.g., Panasonic EEU-FR1C102) placed ≤5mm from VOUT pin per layout guidelines in AP02001.

How does thermal resistance impact heatsink selection for AP1084TL-U at 5A?

With θ_JA = 78°C/W and 5A load at 5V input, power dissipation reaches (5V − 3.3V) × 5A = 8.5W. To hold T_J ≤ 125°C at 25°C ambient, total thermal resistance (θ_JA) must be ≤ (125 − 25)/8.5 ≈ 11.8°C/W - meaning the heatsink + interface must contribute ≤ 11.8 − 78 = negative value, confirming mandatory external heatsink. A 3°C/W heatsink with thermal grease reduces T_J to ~85°C.