onsemi MC34063AMELG

Overview

MC34063AMELG from onsemi is a monolithic DC-DC switching regulator IC supporting step-up, step-down, and inverting topologies. It integrates a temperature-compensated 1.25 V reference (±2%), 1.5 A output switch, current-limit sensing (300 mV typ), oscillator up to 100 kHz, and comparator - requiring only five external components for basic operation. It operates from 3.0 V to 40 V input and delivers stable regulation in industrial power supplies and battery-powered converters.

For engineers reviewing the MC34063AMELG datasheet, pinout, applications, or equivalent options, this page provides verified pin functions, real-world converter performance data (e.g., 87.7% efficiency in step-up mode at 12 V→28 V/175 mA), thermal limits (T_J = +150°C), SOIC-8 package dimensions, and two validated alternative parts with documented functional trade-offs.

Technical Context

The MC34063AMELG implements a fixed-frequency, current-mode control architecture using an internal Darlington output switch and active current-limit circuit. Its oscillator frequency is set by an external timing capacitor (CT) and scales linearly with V_CC, enabling precise duty-cycle control across input ranges.

It supports three fundamental topologies via external component reconfiguration: step-up (boost), step-down (buck), and voltage-inverting (buck-boost). The 1.25 V reference feeds the inverting input of an internal comparator, allowing output voltage adjustment via resistor dividers - confirmed in Figures 9–13 with measured line/load regulation ≤ ±0.12% and ripple < 40 mVpp with filtering.

Key Specifications

Pinout & Package

MC34063AMELG is housed in an 8-pin SOIC package (Case 751, D suffix), with exposed pad not present. Pin functions are validated per Figure 2 and Table "Pin Connections" in the datasheet.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MC34063AMELG, MC34063ADR2G offers identical functionality in optimized packaging for volume manufacturing, while LM2574N-5.0 trades adjustability and current drive for simplicity in fixed-output, lower-power use cases - making it unsuitable as a drop-in replacement but viable for cost-sensitive 5 V-only designs.

Availability

MC34063AMELG is available at Aetrix Electronics and suitable for industrial power supplies, automotive auxiliary rails, portable medical devices, and IoT sensor nodes requiring stable component supply across extended temperature and input voltage ranges.

Supply support for MC34063AMELG 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, and sensor solutions for automotive, industrial, and cloud infrastructure markets.

The MC34063A series was designed as a cost-optimized, general-purpose switching regulator IC family targeting board-level DC-DC conversion in resource-constrained embedded systems - emphasizing minimal external part count and broad input voltage tolerance.

FAQ

What is the maximum output current achievable with MC34063AMELG in step-down configuration?

The MC34063AMELG internal switch supports 1.5 A peak current. In step-down (buck) operation, continuous output current depends on thermal design and duty cycle. As demonstrated in Figure 11, MC34063AMELG delivers 500 mA continuously at 25 V→5 V with 83.7% efficiency and no forced cooling. For higher loads, external transistor boosting (Fig. 10–14) is required - the MC34063AMELG itself remains limited to 1.5 A peak switch current.

Does MC34063AMELG support synchronous rectification?

No, MC34063AMELG does not support synchronous rectification. It uses an internal Darlington bipolar transistor as the main switch and requires an external diode (e.g., 1N5819 Schottky) in all topologies. The datasheet shows no gate-drive outputs or timing signals for controlling an external MOSFET as a synchronous rectifier - only open-collector Driver Collector (Pin 6) for driving external NPN/PNP transistors in current-boost configurations.

Can MC34063AMELG operate from a 2.8 V input supply?

No, MC34063AMELG cannot reliably operate from 2.8 V. Its absolute minimum input voltage is specified as 3.0 V in the "Operation from 3.0 V to 40 V Input" feature list and confirmed in the Maximum Ratings table (V_CC = 40 V max, but no lower limit stated - the 3.0 V value is the guaranteed operational floor). At 2.8 V, internal reference startup, oscillator biasing, and switch drive fall outside specification, risking regulation failure or erratic behavior.

What is the purpose of the EP flag shown in Figure 2 for MC34063AMELG?

The EP flag in Figure 2 is not applicable to MC34063AMELG. That marking appears in the generic SOIC-8 pin diagram (Figure 2 caption notes "(Top View) EP Flag") but refers to packages with exposed pads (e.g., DFN variants). MC34063AMELG uses a standard SOIC-8 (D suffix, Case 751) with no exposed thermal pad - confirmed by package drawings on page 13 and ordering information listing "SOIC−8 (Pb−Free)" without EP designation. The flag is omitted in actual MC34063AMELG marking diagrams.

How does the current limit function in MC34063AMELG, and what resistor value sets 1.0 A trip point?

The MC34063AMELG current limit senses voltage across an external sense resistor (R_SC) connected between Pin 5 (I_PK Sense) and Pin 2 (Switch Emitter). The internal comparator trips when this voltage reaches 300 mV (typical). To set a 1.0 A current limit, use R_SC = 300 mV / 1.0 A = 0.3 Ω. This matches the 0.33 Ω value used in Figure 11's step-down design - confirming the calculation method and validating the 300 mV threshold as the design anchor for overcurrent protection.