Diodes Incorporated AP1184T5-18L-U

Overview

AP1184T5-18L-U from Diodes Incorporated is a 4A ultra-low dropout positive voltage regulator in TO220-5L package, configured for fixed 1.8V output. It delivers 1.8V at up to 4A with 0.85V maximum dropout (Vin–Vout) at full load, built-in thermal shutdown and current limiting, and remote sensing via Vsense pin for precise load regulation-used in GPU core power supplies derived from 3.3V ATX rails.

For engineers reviewing the AP1184T5-18L-U datasheet, AP1184T5-18L-U pinout, AP1184T5-18L-U application, or AP1184T5-18L-U equivalent, key selection criteria include dropout voltage under 4A load, Vctrl supply requirement (>Vout), remote sense capability, thermal resistance (θJA = 31°C/W), and fixed-output stability with ≥100µF output capacitance.

Technical Context

The AP1184T5-18L-U uses an NPN pass transistor architecture with externally supplied Vctrl pin (≥Vout+1V typical), enabling lower dropout than standard PNP LDOs without base-current penalty. Its dual-input flexibility allows Vctrl to be sourced from a higher rail (e.g., 5V) while Vin comes from 3.3V, optimizing efficiency in multi-rail systems.

It implements true remote sensing via dedicated Vsense pin, compensating for PCB trace IR drop between regulator and load. The internal 1.25V reference and adjustable feedback path (not used in fixed 1.8V variant) support tight initial accuracy (±2% over temperature) and fast transient response (<500ns load step recovery).

Key Specifications

Pinout & Package

AP1184T5-18L-U is housed in a TO220-5L package with exposed tab electrically connected to Vout for thermal conduction and low-inductance output return. The tab must be mounted to a heatsink or copper pour per Diodes Inc. layout AP02001.

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, AP1186T5-18L-U offers higher current headroom and lower dropout but identical footprint, while TPS7A8300RGRT adds digital control and smaller size at the cost of remote sensing and analog simplicity.

Availability

AP1184T5-18L-U is available at Aetrix Electronics and suitable for GPU core power supplies, ATX motherboard VRM stages, industrial FPGA I/O banks, and test equipment power rails requiring stable component supply with lead-free compliance and TO220 thermal management.

Supply support for AP1184T5-18L-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 power management, signal integrity, and protection solutions for computing, industrial, and consumer markets.

The AP1184 product line delivers ultra-low-dropout linear regulators optimized for high-current, low-voltage applications in graphics subsystems and motherboard power delivery-designed to replace switching regulators where noise and complexity must be minimized.

FAQ

What is the minimum required Vctrl voltage for AP1184T5-18L-U to regulate properly?

Vctrl must be at least 1V greater than Vout (i.e., ≥2.8V) across the full operating temperature range and load condition. At 25°C and 4A load, typical Vctrl is 4.3V; operation below 2.8V causes loss of regulation and uncontrolled output collapse. This requirement ensures sufficient base drive for the NPN pass transistor under worst-case conditions.

Can AP1184T5-18L-U be used without remote sensing (Vsense tied to Vout)?

Yes-Vsense may be directly connected to Vout for local regulation, but doing so forfeits remote-sense accuracy. Load regulation degrades from 15–18 mV to ~25 mV over 0–4A due to uncompensated PCB trace resistance. For GPU or FPGA applications where voltage must be held at the die, Vsense must route separately to the load point.

Why does AP1184T5-18L-U require both Vin and Vctrl inputs instead of a single supply?

The dual-input architecture separates power delivery (Vin) from control bias (Vctrl) to minimize pass transistor power loss. Vctrl powers the internal error amplifier and base driver independently, allowing it to be sourced from a higher-efficiency rail (e.g., 5V) while Vin comes from the lower 3.3V rail-reducing total dissipation by up to 30% versus single-supply LDOs.

Is AP1184T5-18L-U recommended for new designs according to Diodes Incorporated?

No-Diodes Incorporated marks AP1184 as "NOT RECOMMENDED FOR NEW DESIGN" in its official documentation (Rev. 6, October 2014). This reflects obsolescence planning; however, the part remains actively manufactured and supported for legacy system repair, replacement, and continuity programs through authorized channels including Aetrix Electronics.