Diodes Incorporated AP1186K5-18L-U

Overview

AP1186K5-18L-U from Diodes Incorporated is a 1.5A ultra-low dropout positive voltage regulator in TO263-5L package, fixed at 1.8V output, with 0.38V max dropout at 1.5A load, 70dB ripple rejection, and remote sensing capability via Vsense pin. It delivers stable power to GPU core supplies requiring tight transient response and precise 1.8V rails from 3.3V ATX sources.

For engineers reviewing the AP1186K5-18L-U datasheet, AP1186K5-18L-U pinout, AP1186K5-18L-U application, or AP1186K5-18L-U equivalent, key selection criteria include dropout voltage under full load, thermal resistance (ΘJC = 2.5°C/W), remote-sense stability, control-pin biasing requirements, and compatibility with high-ESR electrolytic output capacitors.

Technical Context

The AP1186K5-18L-U uses an NPN pass transistor architecture with externally biased Vctrl pin-separate from Vin-to eliminate base-current losses typical of PNP LDOs. Its five-terminal topology enables true remote voltage sensing at the load via dedicated Vsense and Adj pins, decoupling regulation accuracy from PCB trace IR drop.

It operates with dual input rails: Vin supplies the pass element while Vctrl powers internal circuitry and drives the transistor base. This allows efficient operation when 3.3V and 5V rails coexist-as on ATX motherboards-enabling 1.8V GPU core supply with <0.4V dropout and fast transient recovery for nanosecond-scale current steps.

Key Specifications

Pinout & Package

AP1186K5-18L-U is housed in a surface-mount TO263-5L (D²PAK) package with exposed tab electrically connected to Vout for thermal conduction and low-inductance output return.

Key Features

Applications

Equivalent & Alternatives

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

Compared with TPS7A4700RGWR and NCP1117DT18T5G, AP1186K5-18L-U uniquely balances 1.5A current, sub-0.4V dropout, remote sensing, and dual-rail flexibility-making it the only option validated for GPU core supply in ATX systems requiring both precision and power density.

Availability

AP1186K5-18L-U is available at Aetrix Electronics and suitable for GPU core power delivery, ATX motherboard auxiliary rails, and industrial FPGA I/O regulation requiring stable component supply, RoHS-compliant packaging, and lead-free assembly compatibility.

Supply support for AP1186K5-18L-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-reliability power management, signal integrity, and protection solutions for computing, industrial, and automotive markets.

The AP1186 series belongs to Diodes' high-current LDO portfolio, engineered specifically for graphics-intensive computing platforms where ultra-low dropout, remote sensing, and dual-input rail efficiency are critical to system-level power architecture.

FAQ

What is the minimum input voltage required for AP1186K5-18L-U to regulate at 1.5A?

The absolute minimum input voltage is V_out + dropout = 1.8V + 0.38V = 2.18V. However, per datasheet test conditions, stable operation at full 1.5A load requires V_in ≥ 3.3V (for 1.8V output) to ensure sufficient headroom for line and load transients, control pin biasing (V_ctrl ≥ V_out + 1V), and thermal margin. Below 3.3V, current capability degrades rapidly due to thermal limiting.

Can AP1186K5-18L-U be used without remote sensing?

Yes-Vsense can be shorted directly to Vout at the regulator pins for local regulation. However, doing so forfeits the primary advantage of the device: compensation for PCB trace resistance. In that configuration, output accuracy degrades by up to 50mV per 50mΩ of trace impedance between regulator and load, making it unsuitable for GPU or high-speed FPGA applications where load-point accuracy is specified.

Why does AP1186K5-18L-U require a separate Vctrl pin instead of using Vin for internal bias?

The Vctrl pin powers the internal control circuitry and base drive independently of the pass transistor's Vin rail. This eliminates base-current dependency on the output load, reducing power loss and improving efficiency-especially critical in high-current LDOs. It also allows optimal biasing (e.g., 5V Vctrl with 1.8V Vout) even when Vin is only marginally above Vout, which would otherwise starve internal circuitry in conventional single-rail LDOs.

Is AP1186K5-18L-U compatible with standard 100µF aluminum electrolytic capacitors?

Yes-the AP1186K5-18L-U is explicitly designed for stability with 100–1000µF aluminum electrolytics having 50–100mΩ ESR. Its compensation network leverages the inherent RC time constant of these capacitors, eliminating the need for low-ESR ceramics or complex external compensation networks. This reduces BOM cost and improves reliability in high-temperature environments where polymer or tantalum caps may degrade.