Diodes Incorporated AP1507-33D5L-U

Overview

AP1507-33D5L-U from Diodes Incorporated is a monolithic 150 kHz, 3A non-synchronous PWM buck DC/DC converter with fixed 3.3V output, integrated power switch, internal compensation, and thermal/current protection. It operates from 4.5V to 22V input, delivers ±4% output voltage accuracy at 3.3V, and supports logic-level ON/OFF shutdown. Used in compact on-card power supplies for embedded microcontrollers and industrial sensors.

For engineers reviewing the AP1507-33D5L-U datasheet, AP1507-33D5L-U pinout, AP1507-33D5L-U application, or AP1507-33D5L-U equivalent, key selection criteria include its fixed 3.3V output, TO-252-5L thermal performance (θ_JA = 50°C/W), 75% efficiency at 12V_IN/3A, and built-in current limit (4.5A typ) with frequency foldback under overload.

Technical Context

The AP1507-33D5L-U implements voltage-mode PWM control with a 1.235V internal reference and fixed 150 kHz oscillator (±15%). Its feedback loop uses the FB pin to regulate output by comparing a resistive divider (not required for fixed 3.3V version) against the reference, enabling stable line/load regulation without external compensation components.

Protection functions include cycle-by-cycle current limiting (triggered at 4.5A typ), thermal shutdown at ~150°C junction temperature, and frequency reduction to 10–50 kHz when V_FB drops below 0.5V during overcurrent. The SD pin accepts 0–1.3V (ON) or ≥2.0V (OFF) logic-level signals for <150 µA standby current.

Key Specifications

Pinout & Package

AP1507-33D5L-U is housed in a lead-free, RoHS-compliant TO-252-5L (DPAK) surface-mount package with exposed metal tab for thermal conduction to PCB copper. The tab is internally connected to GND and must be soldered to ≥2 cm² of 2 oz. copper for rated 3A performance.

Key Features

Applications

Equivalent & Alternatives

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

Compared with LM2596S-3.3/NOPB, AP1507-33D5L-U reduces component count via internal compensation; versus MP1584EN-LF-Z, it trades higher frequency for robustness in noisy industrial environments and simpler thermal management.

Availability

AP1507-33D5L-U is available at Aetrix Electronics and suitable for industrial sensor nodes, embedded microcontroller core supplies, on-card telecom interfaces, and POS terminal main rail conversion requiring stable component supply, long-term lifecycle support, and RoHS-compliant packaging.

Supply support for AP1507-33D5L-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 industrial, computing, and consumer markets.

The AP1507 series targets cost-sensitive, high-reliability DC/DC conversion in space-constrained applications where integration, thermal resilience, and minimal external components are critical design goals.

FAQ

What is the minimum input voltage required for reliable 3.3V output at 3A?

The AP1507-33D5L-U requires a minimum input voltage of 5.5V to maintain regulation at full 3A load, per the datasheet's recommended operating condition. Below this, dropout occurs due to the internal switch saturation voltage (~1.6V) and feedback headroom. For 3.3V output, VIN must exceed V_OUT + V_SAT ≈ 4.9V, with 5.5V specified to ensure margin across temperature and process variation.

Can the FB pin be left floating in the fixed 3.3V version?

Yes-the FB pin is internally connected to the 1.235V reference and output divider in fixed-output variants like AP1507-33D5L-U. Datasheet Section 5 explicitly states FB is "not used" and must remain unconnected. Floating it poses no risk; adding external components would disrupt regulation and is prohibited.

How does thermal performance change with PCB copper area?

θ_JA drops from 50°C/W (2 cm² copper) to ~35°C/W with ≥6 cm² of 2 oz. copper, improving 3A thermal margin by ~15°C. Beyond 6 cm², gains diminish sharply. The metal tab must be soldered directly to this copper; thermal vias to inner layers further reduce θ_JA by ~5–10°C if spaced ≤2 mm apart.

Is the SD pin compatible with 3.3V logic microcontrollers?

Yes-SD accepts logic-high up to 18V, so a 3.3V GPIO can directly drive it into shutdown mode (VIH ≥ 2.0V). For enable, the MCU pulls SD to GND or ≤1.3V. No level shifter is needed, and leakage current is <0.1 µA, ensuring negligible impact on MCU I/O drive capability.