Diodes Incorporated AP1117D33L-U

Overview

AP1117D33L-U from Diodes Incorporated is a 1A low-dropout linear voltage regulator in fixed 3.3V output mode, housed in a TO252-3L surface-mount package. It delivers stable regulation with ≤1.4V dropout at full load, supports input voltages from 4.8V to 12V, and features built-in thermal shutdown and current limiting - ideal for powering 3.3V logic supplies in PC peripherals and VGA cards.

For engineers reviewing the AP1117D33L-U datasheet, AP1117D33L-U pinout, AP1117D33L-U application, or AP1117D33L-U equivalent, key selection considerations include dropout voltage under 1A load, thermal resistance (θ_JA = 73°C/W), output stability with 10µF–22µF tantalum/low-ESR capacitors, and RoHS-compliant lead-free packaging.

Technical Context

The AP1117D33L-U implements a bandgap-referenced error amplifier driving an NPN pass transistor, enabling fast transient response and high ripple rejection (60–70 dB at 180 Hz). Its fixed-output architecture eliminates external resistor networks, simplifying layout for space-constrained applications.

Thermal protection activates at 150°C junction temperature, cycling output off/on during overtemperature events. Load regulation remains within ±33 mV across 0–1A output current at 5V input, and line regulation stays below 0.2% over its specified input range.

Key Specifications

Pinout & Package

AP1117D33L-U uses the TO252-3L (DPak) thermally enhanced surface-mount package, with the exposed tab electrically connected to V_OUT for improved heat transfer to the PCB copper pour.

Key Features

Applications

Equivalent & Alternatives

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

Compared with AP1117E33L-13, the D33L-U's TO252-3L package provides 32% lower θ_JA, enabling full 1 A operation on standard PCBs; versus MIC29302WU-3.3, it trades peak current capability for significantly lower quiescent current and cost in 1 A applications.

Availability

AP1117D33L-U is available at Aetrix Electronics and suitable for PC peripheral designs, VGA card power delivery, and industrial control I/O modules requiring stable component supply, long-term lifecycle support, and RoHS-compliant manufacturing.

Supply support for AP1117D33L-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 was designed specifically for cost-sensitive, space-constrained applications needing robust 1 A LDO regulation - including PC add-in cards, graphics subsystems, and embedded peripheral interfaces.

FAQ

What is the minimum input voltage required for AP1117D33L-U to maintain regulation?

The AP1117D33L-U requires VIN ≥ VOUT + 1.3 V to regulate properly, meaning minimum input is 4.6 V. However, datasheet specifications guarantee performance only above 4.8 V due to margin for worst-case dropout (1.4 V) and line regulation. Below 4.8 V, output may drop out of regulation under full load or elevated temperature.

Can AP1117D33L-U be used with ceramic output capacitors?

Yes, but only with careful ESR consideration: the device requires 0.15–20 Ω effective series resistance for stability. Standard X7R/X5R ceramics typically fall below 0.01 Ω ESR and may cause oscillation. Use either a ceramic capacitor with added series resistor (≈5–10 Ω) or a hybrid approach combining ceramic with a small tantalum or polymer capacitor to meet ESR requirements.

Is the thermal tab of AP1117D33L-U electrically connected, and how should it be handled on the PCB?

Yes, the exposed thermal tab is internally connected to VOUT (Pin 2). It must be soldered to a dedicated copper pour tied directly to the 3.3 V output net - not to ground or floating. This connection provides both thermal conduction and electrical continuity; isolating or grounding the tab will cause malfunction or damage.

Does AP1117D33L-U support reverse-voltage protection or input surge tolerance?

No. The AP1117D33L-U lacks internal reverse-polarity or overvoltage protection. Applying reverse voltage (> −0.3 V) or input transients exceeding 18 V absolute maximum rating risks permanent damage. External protection - such as a series Schottky diode or TVS clamp - must be added if the application exposes VIN to such conditions.