onsemi MC78L15ACD

Overview

MC78L15ACD from onsemi is a 15 V, 100 mA fixed-output linear voltage regulator in SOIC-8 package, featuring internal short-circuit current limiting, thermal shutdown, and no external components required for basic operation. It delivers stable DC power to low-power analog circuits, microcontroller peripherals, and sensor interfaces where input-to-output differential ≥2.0 V is maintained.

For engineers reviewing the MC78L15ACD datasheet, pinout, applications, or equivalent options, key selection criteria include its 15 V ±4% output tolerance at +25°C, 1.7 V dropout voltage, 34–39 dB ripple rejection at 120 Hz, and operation over 0°C to +125°C junction temperature range.

Technical Context

The MC78L15ACD implements a monolithic series-pass regulator architecture with built-in thermal overload protection and foldback current limiting. Its internal circuitry includes a precision voltage reference, error amplifier, and Darlington pass transistor - all integrated into a single silicon die.

It operates as a three-terminal positive regulator requiring only input, ground, and output connections. Stability is ensured without external compensation capacitors under typical conditions, though 0.33 µF input and 0.1 µF output bypass capacitors are recommended for improved transient response and high-frequency noise suppression.

Key Specifications

Pinout & Package

MC78L15ACD uses the SOIC-8 (Case 751) package with internally modified lead frame: pins 2, 3, 6, and 7 are electrically common to the die attach flag for enhanced thermal performance. Thermal resistance is board-dependent (see Figure 8).

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar fixed-voltage linear regulator applications.

Compared with MC78L15ACP and LM78L15ACZ, the MC78L15ACD offers superior thermal performance via its multi-ground SOIC-8 construction, tighter 15 V ±4% output tolerance, and lower output noise - making it optimal for industrial analog signal chains where stability and noise margin are critical.

Availability

MC78L15ACD is available at Aetrix Electronics and suitable for industrial sensor conditioning, microcontroller auxiliary power, legacy I/O module design, and test equipment bias rails requiring stable component supply across extended product lifecycles.

Supply support for MC78L15ACD 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 manufacturer specializing in energy-efficient power, analog, sensor, and connectivity solutions for automotive, industrial, cloud, and consumer markets.

The MC78L00A Series was designed specifically for cost-sensitive, low-power industrial and commercial applications requiring rugged, drop-in fixed-voltage regulation without external compensation.

FAQ

What is the maximum input voltage rating for the MC78L15ACD?

The MC78L15ACD has an absolute maximum input voltage of 35 V for 12–18 V-rated versions and 40 V for 24 V-rated variants; however, per the datasheet's Absolute Maximum Ratings table, the MC78L15ACD (15 V version) is rated for up to 35 Vdc input. Exceeding this risks permanent damage due to junction breakdown or thermal runaway.

Does the MC78L15ACD require external capacitors to operate stably?

The MC78L15ACD does not require external capacitors for basic stability, but the datasheet recommends a 0.33 µF input capacitor (placed close to pins 4 and 2/3) and a 0.1 µF output capacitor (across pins 1 and 2/3) to improve transient response and high-frequency noise immunity - especially when input wiring is long or load capacitance is large.

What is the thermal resistance (R_JA) of the MC78L15ACD in SOIC-8 package?

The MC78L15ACD's thermal resistance is not fixed - it depends on PCB copper area. Figure 8 shows R_JA ranging from ~100°C/W (with 30 mm × 30 mm 2-oz copper) down to ~60°C/W (with optimized thermal pad layout). The SOIC-8's internal flag connection (pins 2/3/6/7) enables significantly better heat transfer than standard SOIC-8 packages.

Can the MC78L15ACD be used as a current source?

Yes - the MC78L15ACD can be configured as a constant-current source by connecting its output to the load and returning the load to ground through a sense resistor to the input, as shown in Figure 9. In this configuration, output current equals (15 V − V_BE) / R, where V_BE ≈ 0.7 V; thus, for 100 mA, R = 143 Ω. Dissipation must be checked per application.

Is the MC78L15ACD pin-compatible with other MC78LxxA variants in SOIC-8?

Yes - all MC78LxxA devices in SOIC-8 (e.g., MC78L05ACD, MC78L12ACD, MC78L15ACD) share identical pinouts (pin 1 = V_OUT, pin 4 = V_IN, pins 2/3/5/6/7 = GND, pin 8 = NC), enabling footprint reuse across output voltages in the same family.