Diodes Incorporated AP1184K5-18L-U

Overview

AP1184K5-18L-U from Diodes Incorporated is a 4A ultra-low dropout positive voltage regulator in TO263-5L package, configured for fixed 1.8V output. It delivers 1.8V at up to 4A with maximum 0.85V dropout (Vin–Vout) at full load, built-in thermal shutdown and current limiting, and supports remote sensing via Vsense pin for precise load regulation. It targets GPU core power delivery from 3.3V ATX rails in graphics card designs.

For engineers reviewing the AP1184K5-18L-U datasheet, AP1184K5-18L-U pinout, AP1184K5-18L-U application, or AP1184K5-18L-U equivalent, key selection criteria include dropout voltage under 4A load, thermal resistance (θJA = 61°C/W), remote sense capability, fixed 1.8V accuracy (±2%), and TO263-5L thermal performance with ≥2 oz copper PCB layout.

Technical Context

The AP1184K5-18L-U uses an NPN-based pass transistor architecture with separate Vctrl and Vsense pins to decouple control biasing from input supply, enabling sub-1V dropout while avoiding base-current losses typical of PNP regulators. Its five-terminal topology allows independent optimization of control loop stability (via 100µF capacitor on Vctrl) and output regulation (via 100µF on Vout).

It implements true remote voltage sensing by comparing Vsense directly to the internal 1.25V reference, compensating for IR drop across PCB traces. The device operates with Vin ≥ 2.5V for 1.8V output and requires Vctrl ≥ Vin + 1V to maintain regulation - a design constraint critical for dual-rail motherboard implementations.

Key Specifications

Pinout & Package

AP1184K5-18L-U is housed in a surface-mount TO263-5L (D²PAK) package with exposed thermal pad (Tab = Vout). The package supports high-power dissipation when mounted on ≥2 oz copper PCB per Diodes' AP02001 layout guidelines.

Key Features

Applications

Equivalent & Alternatives

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

Compared with AP1184T5-18L-U, the K5 variant offers superior SMT manufacturability and smaller footprint; versus TPS7A8300RGRT, it trades PSRR for essential remote sensing capability critical in long-trace GPU applications.

Availability

AP1184K5-18L-U is available at Aetrix Electronics and suitable for GPU core power supply, ATX motherboard VRM staging, industrial FPGA I/O bank regulation, and embedded vision processor core supply requiring stable component supply across production lifecycles.

Supply support for AP1184K5-18L-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-performance power management, signal integrity, and protection solutions for computing, industrial, and consumer markets.

The AP1184 product line delivers ultra-low dropout linear regulators targeting high-current, low-voltage applications in graphics and computing platforms where efficiency, thermal performance, and remote sensing are critical.

FAQ

What is the minimum required Vctrl voltage for AP1184K5-18L-U to regulate properly?

Vctrl must be at least 1V higher than Vin to ensure proper base drive for the NPN pass transistor. For a 3.3V input, Vctrl ≥ 4.3V is required. This is not a headroom above Vout but a fixed offset above Vin, as confirmed in the Electrical Characteristics table and Functional Descriptions section.

Can AP1184K5-18L-U operate without the Vsense connection?

Yes - Vsense may be shorted to Vout for local regulation, but doing so forfeits remote sensing capability. The device will still regulate at 1.8V with typical load regulation of 18 mV, but trace resistance between regulator and load will cause uncorrected voltage drop at the load point.

Is AP1184K5-18L-U recommended for new designs?

No - the datasheet explicitly states "NOT RECOMMENDED FOR NEW DESIGN" (Rev. 6-3, October 2014). This reflects obsolescence status; Diodes recommends newer alternatives like the AP7361 series for new projects, though AP1184K5-18L-U remains supported for legacy production and repair.

What output capacitor value is mandatory for stability with AP1184K5-18L-U?

A minimum 100 µF aluminum electrolytic capacitor with ESR between 50–100 mΩ is required on the Vout pin. This value is specified in the Stability section and validated across temperature and load conditions; lower values risk oscillation or poor transient response.