onsemi MC33565D

Overview

MC33565D from onsemi is a smart dual-input low-dropout voltage regulator designed for PCI/NIC peripheral card power management, delivering a precisely regulated 3.3 V output at up to 200 mA while enabling glitch-free transitions between 5.0 V "active" and 3.3 V "sleep" system modes. It integrates internal logic for supply detection, a low-noise LDO regulator, and a dedicated switch drive output for external P-channel MOSFET control.

For engineers reviewing the MC33565D datasheet, pinout, applications, or equivalent options, this device addresses critical requirements in ACPI-compliant hot-swap power sequencing, reverse-current blocking during auxiliary-mode operation, and tight ±2% output regulation over −5°C to +150°C junction temperature.

Technical Context

The MC33565D implements a dual-supply architecture with an internal low-dropout linear regulator active when the main 5.0 V input exceeds 4.02 V (lower threshold), and automatic bypass via external P-MOSFET when the main input falls below that level. Its integrated low-voltage detector provides 150 mV hysteresis (4.02 V/4.17 V thresholds) for noise-immune mode switching.

It features active sense-input feedback for load-independent regulation, thermal shutdown at ~170°C, current limiting at 730 mA typical, and reverse leakage <25 µA from output to main input - all while maintaining output voltage ≥3.0 V across full operating conditions.

Key Specifications

Pinout & Package

MC33565D is housed in an SOIC-8 (Case 751) package with 1.27 mm pitch, 4.9 mm × 3.9 mm body, and exposed pad not present. Pins 2 and 5 are NC (no internal connection).

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar dual-input voltage regulator applications.

Compared with NCP33565DR2G, MC33565D offers identical performance in Pb-containing assembly; versus TPS2113APWR, MC33565D integrates regulation and detection logic, eliminating external components and simplifying layout for 200 mA peripheral card use cases.

Availability

MC33565D is available at Aetrix Electronics and suitable for PCI/NIC card designs, industrial I/O modules, and laptop docking station peripherals requiring stable component supply with guaranteed long-term sourcing.

Supply support for MC33565D 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

onsemi (formerly ON Semiconductor) is a global semiconductor supplier specializing in energy-efficient power management, analog, sensor, and connectivity solutions for automotive, industrial, cloud, and consumer markets.

The MC33565D belongs to onsemi's Smart Power Regulator family, engineered specifically for ACPI-compliant peripheral card power sequencing where glitch-free transitions between 5 V and 3.3 V domains are essential.

FAQ

What is the primary function of the MC33565D in a peripheral card design?

The MC33565D serves as an intelligent dual-input voltage regulator that automatically selects between a 5.0 V main supply and a 3.3 V auxiliary supply to deliver a stable 3.3 V output at up to 200 mA. Its core function is to ensure uninterrupted power during sleep-to-active transitions in PCI/NIC cards, as required by ACPI standards. The MC33565D achieves this through integrated low-voltage detection, internal LDO regulation, and dedicated switch drive for external P-MOSFET control - all in a single SOIC-8 package.

Does the MC33565D require external compensation components?

Yes, the MC33565D requires an external compensation capacitor of minimum 4.7 µF connected between pins 6 (Sense Input) and 7 (Regulator Output). This capacitor stabilizes the feedback loop and ensures phase margin >45° across operating conditions. The datasheet specifies maximum ESR of 500 mΩ; tantalum or low-ESR polymer capacitors are recommended. Omitting or undersizing this capacitor risks oscillation and poor transient response. The MC33565D does not operate reliably without it.

Can pins 2 and 5 of the MC33565D be used for grounding or signal routing?

No - pins 2 and 5 of the MC33565D are explicitly designated as NC (no connection) and are not internally bonded. The datasheet states "Pins 2 and 5 are not internally connected," and the functional block diagram confirms no internal circuitry connects to them. Routing traces to or from these pins may introduce parasitic coupling or contamination risk. For reliable operation, leave pins 2 and 5 unconnected and avoid solder mask openings or copper pours beneath them. This applies strictly to the MC33565D SOIC-8 variant.

How does the MC33565D prevent reverse current flow during sleep mode?

The MC33565D prevents reverse current flow using its internal NPN pass transistor architecture and controlled gate drive. When the main 5.0 V input drops below 4.02 V, the internal LDO shuts off and the switch drive (pin 8) goes low, turning on the external P-MOSFET to supply the load from the 3.3 V auxiliary rail. Crucially, the internal pass device blocks conduction from the 3.3 V output back into the main input - measured leakage is ≤25 µA. This eliminates backfeed that could destabilize upstream power supplies. The MC33565D achieves this without external diodes or controllers.

What is the thermal shutdown behavior of the MC33565D?

The MC33565D activates thermal shutdown at approximately 170°C junction temperature, disabling the output until temperature decreases. Unlike many regulators, it has no built-in hysteresis - so repeated on/off cycling ("oscillation") occurs if heat dissipation is insufficient. This behavior protects against catastrophic failure but is not a substitute for proper PCB layout: the SOIC-8 package has RθJA = 146°C/W, requiring adequate copper area and airflow. Thermal shutdown triggers independently of current limit and affects both LDO and switch drive outputs. The MC33565D resumes normal operation only after junction temperature falls significantly below the trip point.