onsemi MC78L12ACD

Overview

MC78L12ACD from onsemi is a 12 V, 100 mA fixed-output linear voltage regulator in SOIC-8 package, featuring internal short-circuit current limiting, thermal shutdown, and dropout voltage of 1.7 V at 25°C. It operates over 0°C to +125°C junction temperature and requires no external components for basic regulation in low-power analog or digital supply rails.

For engineers reviewing the MC78L12ACD datasheet, pinout, applications, or equivalent options, key selection criteria include output voltage tolerance (±4.2% at 25°C), load regulation (≤50 mV over 1–40 mA), ripple rejection (42 dB at 120 Hz), thermal resistance (R_JA per Figure 8), and SOIC-8 lead-frame thermal enhancement.

Technical Context

The MC78L12ACD implements a monolithic series-pass regulator with PNP pass transistor, error amplifier, reference, and protection circuitry integrated on a single die. Its SOIC-8 package (Case 751) features internally commoned pins 2, 3, 6, and 7 tied to the die attach flag to reduce thermal resistance.

It delivers stable 12 V output across input voltages from 14.5 V to 27 V DC, with line regulation ≤200 mV and load regulation ≤50 mV under specified conditions. Dropout is defined as the input-output differential where output drops 2% below nominal - measured at 1.7 V typical.

Key Specifications

Pinout & Package

MC78L12ACD uses an SOIC-8 package (Case 751, D Suffix) with internally modified lead frame: pins 2, 3, 6, and 7 are electrically common to the die attach flag for improved thermal performance. No heatsink required for typical power dissipation.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MC78L12ACP (TO-92) and LM78L12ACZ (SOIC-8), the MC78L12ACD offers superior thermal performance via its enhanced SOIC-8 lead-frame design, enabling higher sustained current in compact layouts without heatsinking - critical for dense industrial PCBs.

Availability

MC78L12ACD is available at Aetrix Electronics and suitable for industrial sensor interfaces, legacy microcontroller power, point-of-load regulation, and LED driver bias supply requiring stable component supply and long-term manufacturability.

Supply support for MC78L12ACD 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 delivering energy-efficient, intelligent power and sensing solutions for automotive, industrial, cloud, medical, and IoT applications.

The MC78L00A Series was designed as a cost-optimized, rugged fixed-output linear regulator family for general-purpose analog and digital supply rails where simplicity, reliability, and wide operating temperature range matter more than ultra-low noise or ultra-high PSRR.

FAQ

What is the maximum input voltage rating for MC78L12ACD?

The absolute maximum input voltage for MC78L12ACD is 35 V DC for 12 V output variants, as specified in the Absolute Maximum Ratings table. Operation above 27 V is not recommended for reliable regulation, and sustained input above 30 V risks device damage even if within absolute limits.

Does MC78L12ACD require input and output capacitors for stability?

MC78L12ACD does not require output capacitance for stability, but a 0.1 µF ceramic capacitor is recommended to improve transient response. An input bypass capacitor (≥0.33 µF) is advised if the regulator is located >5 cm from the power supply filter or driving large capacitive loads.

What is the thermal resistance (R_JA) of MC78L12ACD in SOIC-8 package?

MC78L12ACD's R_JA is not fixed - it depends on PCB copper area per Figure 8. With 170 mm² (2.64 in²) of 2 oz. copper, R_JA drops to ~100°C/W; with minimal copper, it approaches 190°C/W. The SOIC-8's internal lead-frame modification lowers thermal resistance versus standard SOIC-8.

Can MC78L12ACD be used as a current source?

Yes - MC78L12ACD can be configured as a constant-current source by connecting a resistor between output and adjust/reference node (though not explicitly labeled as such). Per Figure 9 in the datasheet, it functions similarly to other MC78LxxA devices: output current I_O ≈ V_REF/R, where V_REF ≈ 12 V.

Is MC78L12ACD pin-compatible with LM78L12ACZ?

Yes - MC78L12ACD and LM78L12ACZ share identical SOIC-8 pinout (pin 1 = output, pin 4 = input, pins 2/3/5/6/7/8 = ground), same footprint, and functionally equivalent electrical behavior. Both meet JEDEC MS-012 standards, enabling direct substitution in most designs without layout changes.