onsemi MC34063AP1G

Overview

MC34063AP1G from onsemi is a monolithic DC-DC converter controller IC designed for step-down (buck), step-up (boost), and voltage-inverting applications. It integrates a temperature-compensated 1.25 V reference, comparator, oscillator with active current limiting, driver, and 1.5 A high-current output switch. Its 3.0–40 V input range, adjustable output voltage, and 100 kHz max switching frequency support compact power supply designs in industrial instrumentation and battery-powered systems.

For engineers reviewing the MC34063AP1G datasheet, pinout, applications, or equivalent options, key selection considerations include its Darlington output stage saturation voltage (1.0–1.3 V at 1.0 A), precision 2% reference tolerance, thermal resistance of 115 °C/W in PDIP-8, and compatibility with external NPN/PNP switches for >1.5 A peak current handling.

Technical Context

The MC34063AP1G implements a fixed-frequency, current-mode control architecture using an internal oscillator whose timing capacitor (CT) sets frequency between 24–42 kHz (typical at 33 kHz with 1 nF). Its current-limit sense threshold is tightly specified at 250–350 mV, enabling accurate overcurrent protection without external sensing resistors beyond R_sc.

It operates in three primary topologies: buck (step-down), boost (step-up), and inverting - each requiring only five to seven external components. The internal Darlington output switch eliminates need for external drive circuitry in standard configurations, while pin 7 (driver collector) supports external transistor boosting for higher current or faster switching.

Key Specifications

Pinout & Package

MC34063AP1G uses the PDIP-8 (Plastic Dual In-line Package, Case 626) with 0.3-inch body width and 0.1-inch lead pitch. This through-hole package offers robust thermal performance (R_JA = 115 °C/W) and mechanical stability for prototyping and low-volume production.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar DC-DC controller applications.

Compared with MC34063AP1G, MC34063ADR2G offers identical functionality in a smaller SOIC-8 footprint but trades 30% higher thermal resistance; LM2574N-5.0 sacrifices topology flexibility and current capability for simplicity in fixed-voltage, low-power buck designs.

Availability

MC34063AP1G is available at Aetrix Electronics and suitable for industrial power supplies, battery-powered instruments, voltage-inverting supplies, and automotive aftermarket modules requiring stable component supply and long-term manufacturability.

Supply support for MC34063AP1G 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, and cloud infrastructure markets.

The MC34063A series was engineered as a cost-optimized, general-purpose DC-DC controller family targeting discrete power supply designs where integration, flexibility, and ruggedness outweigh ultra-high efficiency or MHz switching.

FAQ

What is the maximum input voltage rating for the MC34063AP1G?

The MC34063AP1G has an absolute maximum input voltage (V_CC) rating of 40 V DC. This allows it to operate directly from 24 V industrial buses or 36 V nominal battery systems without external pre-regulation. Exceeding 40 V risks permanent damage per the datasheet's Maximum Ratings table. For automotive applications with load dump transients, external clamping may be required to ensure V_CC stays within this limit during fault conditions.

Can the MC34063AP1G be used in boost configuration, and what is the typical efficiency?

Yes, the MC34063AP1G supports boost topology, as validated in Figure 9 of the datasheet delivering 28 V/175 mA from 12 V input at 87.7% efficiency. Efficiency depends on external component selection - particularly inductor DCR, diode forward voltage, and switching frequency - but typically ranges from 83–88% for well-designed 5–25 W boost converters. Lower output currents improve efficiency due to reduced conduction losses in the internal switch.

What is the purpose of Pin 6 (Driver Collector) on the MC34063AP1G?

Pin 6 is an open-collector driver output that controls an external NPN or PNP transistor to extend the peak switch current beyond the internal 1.5 A limit. When used with an external switch, Pin 6 replaces the internal Darlington stage, enabling >2 A peak currents in buck, boost, or inverting topologies. The datasheet shows configurations in Figures 10, 12, and 14, where Pin 6 drives the base of an external transistor while Pins 1 and 2 remain unused.

How does the current limit function work on the MC34063AP1G?

The MC34063AP1G implements cycle-by-cycle current limiting by comparing the voltage across an external sense resistor (R_sc) connected to Pin 5 against an internal 300 mV threshold. When V_Rsc ≥ 300 mV, the oscillator disables the output switch for that cycle. R_sc is calculated as 0.3 / I_pk(max), e.g., 0.2 Ω for 1.5 A peak. This protects both the IC and external magnetics from overcurrent stress during startup or short-circuit events.

Is the MC34063AP1G RoHS compliant and Pb-free?

Yes, the MC34063AP1G is RoHS compliant and Pb-free, as confirmed by the "G" suffix in its part number and explicit statements in the datasheet's Features section and Ordering Information table. It meets EU Directive 2011/65/EU and is halogen-free/BFR-free. The device is suitable for environmentally regulated markets including EU, China, and South Korea, with full compliance documentation available from onsemi's quality portal.