onsemi MC34063AP

Overview

MC34063AP from Fairchild Semiconductor is a monolithic DC-DC switching regulator controller IC used for step-up, step-down, and inverting topologies. It integrates a temperature-compensated 1.24 V reference, oscillator, driver, and 1.5 A output switch, operating from 3.0 V to 40 V input with adjustable output voltage and 100 Hz–100 kHz switching frequency-commonly deployed in battery-powered industrial power supplies.

For engineers reviewing the MC34063AP datasheet, pinout, applications, or equivalent options, key selection criteria include its internal 1.5 A switch current capability, ±5 mV reference voltage line regulation, 300 mV current-limit sense threshold, and DIP-8 package compatibility with legacy through-hole PCB layouts.

Technical Context

The MC34063AP implements a fixed-frequency, current-mode control architecture using an internal oscillator with programmable timing capacitor (CT) and resistor (RT), enabling precise duty-cycle adjustment. Its comparator compares a scaled feedback voltage against a stable 1.24 V reference, while the output switch operates in saturation with V_CE(SAT) ≤ 1.30 V at 1.0 A.

It supports three basic converter configurations without external transistors: buck (step-down), boost (step-up), and buck-boost (inverting). The device's short-circuit protection relies on a 300 mV current-sense threshold across the sense resistor, and standby current remains below 5 mA over full input range.

Key Specifications

Pinout & Package

MC34063AP is housed in an 8-pin dual in-line package (DIP) per JEDEC MS-001, with 0.300-inch body width and 0.100-inch lead pitch. Pin 1 is marked by a notch or dot; leads are tin-lead plated unless RoHS-compliant.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MC33063AP and LM2574N-5.0, the MC34063AP offers unique configurability across all three switching topologies with internal switch and adjustable output, making it optimal for prototyping and multi-rail legacy system upgrades where layout reuse and design flexibility are critical.

Availability

MC34063AP is available at Aetrix Electronics and suitable for portable instrument power supplies, industrial sensor node regulators, and legacy equipment voltage adapters requiring stable component supply and long-term obsolescence management.

Supply support for MC34063AP 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

Fairchild Semiconductor was a U.S.-based semiconductor company specializing in power management, analog, and interface ICs before its acquisition by ON Semiconductor in 2016.

The MC34063A series was designed as a general-purpose, low-cost DC-DC controller for cost-sensitive, medium-power applications where design flexibility and through-hole manufacturability were prioritized over integrated FETs or high-frequency operation.

FAQ

What is the maximum output current achievable with MC34063AP without external transistors?

The MC34063AP features an internal NPN switch rated for 1.5 A peak current. In practical buck or boost configurations with proper thermal management and duty cycle control, sustained output currents up to 750 mA are achievable. The actual limit depends on input/output voltage differential, switching frequency, inductor DCR, and PCB copper area-designs exceeding 500 mA should verify thermal performance using the 1 W DIP package power dissipation rating.

Can MC34063AP be used to generate negative output voltage?

Yes, the MC34063AP supports inverting (buck-boost) topology natively. When configured as an inverter, it generates a regulated negative output from a positive input-e.g., –5 V from +12 V-using standard external components: one inductor, two capacitors, and one diode. The internal switch and comparator operate identically in this mode, with feedback applied to the COMP pin referencing ground.

What is the purpose of the VREF pin (Pin 6) on MC34063AP?

The VREF pin (Pin 6) provides a stable, temperature-compensated 1.24 V reference output derived from the internal bandgap circuit. It is used to bias the feedback resistor divider network connected to the COMP pin, enabling precise output voltage regulation. Unlike many controllers, this reference is actively sourced and can supply limited current (≤100 µA), allowing direct connection to high-impedance dividers without external buffering.

How does the current-limit function work in MC34063AP?

The MC34063AP implements cycle-by-cycle current limiting by monitoring voltage across an external sense resistor connected between Pin 7 (I_SENSE) and ground. When this voltage reaches 300 mV (typical), the internal comparator disables the output switch for that cycle. This hardware-based protection operates independently of the feedback loop and remains active even during startup or fault conditions, preventing damage to the internal switch or external magnetics.

Is MC34063AP RoHS compliant?

Yes, the MC34063AP is RoHS compliant as indicated in the official Fairchild ordering information table, which specifies "RoHS" under Eco Status for this part number. It contains no lead in solder finish beyond RoHS exemptions and meets Directive 2011/65/EU requirements for restricted substances. Full compliance documentation is available in Fairchild's green initiatives portal referenced in the datasheet.