Diodes Incorporated AP1084T18G-U

Overview

AP1084T18G-U from Diodes Incorporated is a 5A low-dropout linear regulator in TO220-3L package, fixed 1.8V output, with 1.4V max dropout at full load, thermal shutdown, and current limiting. It delivers stable 1.8V supply for low-voltage logic such as DDR memory termination and FPGA core rails under 4.7–12V input.

For engineers reviewing the AP1084T18G-U datasheet, AP1084T18G-U pinout, AP1084T18G-U application, or AP1084T18G-U equivalent, key selection criteria include dropout voltage at 5A, thermal resistance (θJA = 78°C/W), output tolerance (±2% at 10mA), stability with ≥10µF output capacitor, and fixed-mode GND-connected ADJ pin configuration.

Technical Context

The AP1084T18G-U operates as a fixed-output LDO with internal 1.25V reference and precision resistor divider network setting VOUT = 1.800V (typ) at 10mA. Its control loop maintains regulation with ≤1.4V VIN–VOUT differential across 0–5A load range and supports fast transient response via optimized compensation requiring only a 10µF output capacitor (ESR 0.15–20Ω).

Thermal protection activates at 150°C junction temperature, and current limiting engages at 5.1A (VIN–VOUT = 5V). The device uses a single NPN pass transistor architecture with integrated error amplifier, reference, and protection circuitry - no external feedback components required in fixed mode.

Key Specifications

Pinout & Package

AP1084T18G-U uses TO220-3L package with exposed thermal tab electrically connected to VOUT. Mounting requires insulated standoff or thermal pad to chassis ground when VOUT is not system ground.

Key Features

Applications

Equivalent & Alternatives

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

Compared with AP1084T18G-U, AP1084T18G-13 offers identical performance in automated assembly format, while TLV1117-18CDCY trades 5A capacity and thermal safety for smaller size - making the AP1084T18G-U optimal for high-current, thermally demanding 1.8V rail designs.

Availability

AP1084T18G-U is available at Aetrix Electronics and suitable for FPGA core power, DDR memory termination, and industrial PLC I/O modules requiring stable component supply with full production lifecycle support.

Supply support for AP1084T18G-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, specializing in high-reliability power management, signal integrity, and protection solutions for industrial, computing, and consumer markets.

The AP1084 product line targets high-current, low-noise linear regulation for digital logic rails - engineered specifically for FPGA, ASIC, and memory subsystems where switching noise and voltage accuracy are critical.

FAQ

What is the minimum input voltage required for AP1084T18G-U to maintain 1.8V regulation at 5A?

The AP1084T18G-U requires VIN ≥ VOUT + 1.4V = 3.2V to regulate at full 5A load. At lighter loads, dropout decreases - e.g., 1.3V at 2.5A per datasheet. Input below 3.2V will cause output collapse proportional to (VIN – 3.2V), with no foldback or current limiting below dropout threshold.

Can AP1084T18G-U be used in adjustable mode?

No - AP1084T18G-U is factory-configured as a fixed 1.8V device. The "18" in the part number denotes fixed 1.8V output; the ADJ pin is internally connected to GND. For adjustable operation, select AP1084T-U (blank suffix) and add external R1/R2 resistors per the VOUT = 1.25(1+R2/R1) formula.

Is a heatsink mandatory for AP1084T18G-U at 5A continuous load?

Yes - at 5A with 5V input (3.2V drop), power dissipation is 16W. With θJA = 78°C/W, junction temperature rise would exceed 1250°C without heatsinking. A minimum 1.5°C/W heatsink is required to hold TJ ≤ 125°C at 5A/5V input; derating is essential for ambient >25°C.

What output capacitor is required for stability with AP1084T18G-U?

A minimum 10µF aluminum or tantalum capacitor with ESR between 0.15Ω and 20Ω is required at the VOUT pin. Diodes Inc. validates stability with 100µF electrolytic (as shown in typical application circuits); ceramic capacitors alone are insufficient due to low ESR causing phase margin loss.