Diodes Incorporated AP1186K5-33L-U

Overview

AP1186K5-33L-U from Diodes Incorporated is a 1.5A ultra-low dropout positive fixed-mode linear regulator with 3.3V output, 0.38V max dropout at 1.5A, TO263-5L package, and built-in thermal shutdown and current limiting. It delivers stable 3.3V supply for graphics chipset power rails fed from 5V/3.3V ATX sources where high efficiency and fast transient response are critical.

For engineers reviewing the AP1186K5-33L-U datasheet, AP1186K5-33L-U pinout, AP1186K5-33L-U application, or AP1186K5-33L-U equivalent, key selection criteria include dropout voltage under full load, remote sensing capability via Vsense pin, thermal resistance (2.5°C/W junction-to-case), control pin (Vctrl) biasing requirements, and minimum output capacitance (100µF).

Technical Context

The AP1186K5-33L-U uses an NPN pass transistor architecture with externally biased Vctrl pin-enabling lower dropout than conventional PNP LDOs while avoiding base-current-related inefficiency. Its dedicated Vsense pin enables true remote voltage sensing at the load, compensating for PCB trace IR drop.

It operates with Vin ≥ 3.8V (for 3.3V output), requires Vctrl > Vout (min 6V recommended), and achieves 70dB ripple rejection at 120Hz. The device maintains ±1% load regulation over 0–1.5A and integrates thermal shutdown triggered above 150°C junction temperature.

Key Specifications

Pinout & Package

AP1186K5-33L-U is housed in a surface-mount TO263-5L (D²PAK) package with exposed tab electrically connected to Vout for thermal conduction. The tab must be soldered to a ≥1.4"×1.4" copper pour 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 AP1186K5-33L-U, the TO220 variant offers identical electrical performance in through-hole form, while the TPS7A4700 trades remote sensing and 1.5A capability for superior high-frequency PSRR-making it better suited for analog signal chains than GPU power delivery.

Availability

AP1186K5-33L-U is available at Aetrix Electronics and suitable for graphics card power delivery, ATX motherboard auxiliary rails, industrial FPGA I/O banks, and medical imaging sensor interfaces requiring stable component supply with RoHS-compliant lead-free packaging.

Supply support for AP1186K5-33L-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 semiconductor company specializing in discrete, analog, and mixed-signal devices, with design and manufacturing operations across Asia and the Americas.

The AP1186 series belongs to Diodes' high-current LDO portfolio, engineered specifically for graphics and computing applications demanding ultra-low dropout, remote sensing, and dual-input flexibility in ATX and embedded platforms.

FAQ

What is the minimum input voltage required for AP1186K5-33L-U to regulate at full 1.5A load?

The datasheet specifies a minimum input voltage of 3.8V for the 3.3V version under 1.5A load, based on a maximum dropout of 0.38V. This ensures regulation margin even at elevated junction temperatures and worst-case process variation. Operating below 3.8V risks dropout and unregulated output.

Can the Vsense pin be left unconnected if remote sensing is not needed?

No-Vsense must be connected directly to the Vout pin in fixed-mode operation. Leaving it floating violates the internal feedback loop and causes instability or regulation failure. The datasheet explicitly requires this connection for all fixed-output variants including AP1186K5-33L-U.

Is a heatsink required for AP1186K5-33L-U in a 1.5A, 3.3V application with Vin = 5V?

With Vin = 5V, Vout = 3.3V, and Iout = 1.5A, power dissipation is ~1.68W. Given θ_JC = 2.5°C/W and typical θ_CA ≈ 40°C/W on 1.4"×1.4" copper, junction temperature rises ~70°C above ambient-well within the 150°C limit. A heatsink is not mandatory but improves margin under sustained load or high ambient conditions.

Why does AP1186K5-33L-U require a separate Vctrl supply instead of deriving bias internally from Vin?

The external Vctrl pin enables independent optimization of the control circuit's supply-allowing use of a cleaner, lower-noise rail (e.g., filtered 3.3V) while Vin carries switching noise from upstream converters. This separation improves PSRR and transient stability, especially critical for graphics loads with nanosecond-scale current steps.