Diodes Incorporated AP1117T18L-U

Overview

AP1117T18L-U from Diodes Incorporated is a 1A low-dropout linear voltage regulator in TO220-3L package, fixed 1.8V output, with ≤1.4V dropout at full load, ±1.2% output voltage accuracy at 10mA, and integrated thermal shutdown. It delivers stable 1.8V supply for low-power logic circuits in PC peripherals and communication modules operating from 3.3V–12V input rails.

For engineers reviewing the AP1117T18L-U datasheet, AP1117T18L-U pinout, AP1117T18L-U application, or AP1117T18L-U equivalent, key selection criteria include dropout voltage under 1A load, thermal resistance (θ_JA = 78°C/W), fixed 1.8V output tolerance, stability with 10µF output capacitor (ESR 0.15–20Ω), and TO220-3L thermal tab mounting requirements.

Technical Context

The AP1117T18L-U implements a bandgap-referenced error amplifier driving an NPN pass transistor, enabling fast transient response to load steps up to 1A. Its internal current limiting and thermal shutdown activate at ≥150°C junction temperature, ensuring safe operation during overload or poor heatsinking.

Designed for fixed-output use, it eliminates external resistor networks-pin 1 is grounded, pin 2 delivers regulated 1.8V, and pin 3 accepts 3.3V–12V input. The device requires only two external capacitors: 10µF input (low-ESR ceramic/tantalum) and 22µF output (tantalum) for stability across 0–125°C operating range.

Key Specifications

Pinout & Package

AP1117T18L-U uses TO220-3L package with exposed thermal tab electrically connected to VOUT (pin 2). Mounting the tab to a heatsink or copper pour is mandatory for thermal management at full 1A load.

Key Features

Applications

Equivalent & Alternatives

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

Compared with LD1117S18TR and TLV1117-18CDCYR, the AP1117T18L-U uniquely combines TO220-3L's superior thermal performance (78°C/W) with full 1A capability and 1.4V dropout-making it the sole option among these three for unheatsinked 1A operation at 70°C ambient.

Availability

AP1117T18L-U is available at Aetrix Electronics and suitable for PC peripheral designs, VGA card manufacturing, industrial sensor interface modules, and communication gateway development requiring stable component supply and long-term industrial lifecycle support.

Supply support for AP1117T18L-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 and computing markets.

The AP1117 series targets cost-sensitive, high-volume applications needing robust fixed-output LDOs with proven thermal safety-designed specifically for PC peripherals, graphics cards, and communication infrastructure where reliability and manufacturability are paramount.

FAQ

What is the minimum input voltage required for AP1117T18L-U to regulate at 1.8V output?

The input voltage must exceed 3.2V to maintain regulation: VIN ≥ VOUT + dropout = 1.8V + 1.4V = 3.2V. At 1A load and 25°C, typical dropout is 1.3V, so 3.1V suffices-but design margin requires 3.2V minimum per datasheet absolute maximum rating.

Can AP1117T18L-U operate without an input capacitor?

No. A minimum 10µF low-ESR ceramic or tantalum capacitor must be placed within 5mm of the VIN pin to prevent oscillation during load transients. Omitting it causes instability, output overshoot, and potential thermal shutdown activation under dynamic load conditions.

Is the thermal tab of AP1117T18L-U electrically isolated?

No. The TO220-3L thermal tab is internally connected to the VOUT (pin 2) terminal. When mounting to a heatsink or PCB copper pour, ensure electrical isolation unless the heatsink is referenced to the 1.8V output rail-otherwise, short-circuit or ground loop risks occur.

Does AP1117T18L-U require a minimum load current to maintain regulation?

Yes. A minimum load of 5–10mA is required across the operating temperature range (0–125°C) to guarantee regulation. Below this, output voltage may rise above 1.8V due to quiescent current limitations; adding a 180Ω bleed resistor to ground satisfies this requirement.