onsemi MC78L09ABD

Overview

MC78L09ABD from onsemi is a 100 mA, fixed +9.0 V positive 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 across −40°C to +125°C and requires no external components for basic regulation in low-power embedded, sensor, and industrial control circuits.

For engineers reviewing the MC78L09ABD datasheet, pinout, applications, or equivalent options, key selection criteria include output voltage tolerance (±5% at 25°C), input voltage range (11.5–24 V), load regulation (≤40 mV over 1–40 mA), and thermal resistance (R_JA per PCB copper area per Figure 8).

Technical Context

The MC78L09ABD implements a monolithic series-pass transistor regulator with bandgap reference, error amplifier, and protection circuitry. Its architecture delivers stable 9.0 V output under line variations (11.5–24 V input) and load changes (1–40 mA), with ripple rejection of 37–57 dB at 120 Hz.

It uses a TO-92-compatible SOIC-8 lead frame (Case 751) with pins 2, 3, 6, and 7 internally commoned to the die attach flag-reducing thermal resistance versus standard SO-8. Junction temperature is limited to 150°C via thermal overload protection.

Key Specifications

Pinout & Package

MC78L09ABD is housed in an SOIC-8 package (Case 751), with pins 2, 3, 6, and 7 electrically connected to the die attach flag for enhanced thermal dissipation. The package conforms externally to standard SO-8 dimensions but features internal lead-frame modification to reduce R_JA.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MC78L09ACDR2G, MC78L09ABD enables cold-start operation in harsh environments; compared with NCV78L09ABDR2G, it offers identical performance at lower cost and without automotive documentation overhead-ideal for industrial BOM optimization.

Availability

MC78L09ABD is available at Aetrix Electronics and suitable for industrial sensor interfaces, automotive body control modules, low-power IoT nodes, and legacy PLC upgrades requiring stable component supply and long-term lifecycle support.

Supply support for MC78L09ABD 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, high-performance silicon solutions for automotive, industrial, cloud, medical, and IoT applications.

The MC78L00A Series-including MC78L09ABD-is designed for cost-sensitive, low-current fixed-voltage regulation in space-constrained and thermally demanding environments where simplicity, ruggedness, and wide temperature operation are critical.

FAQ

What is the maximum input voltage rating for MC78L09ABD?

The absolute maximum input voltage for MC78L09ABD is 35 Vdc when operating in the 12–18 V nominal input range. Exceeding this rating risks permanent device damage, as specified in the Absolute Maximum Ratings table. For reliable operation, maintain input between 11.5 V and 24 V per the Electrical Characteristics section-ensuring sufficient headroom above the 1.7 V dropout while avoiding overstress.

Does MC78L09ABD require input and output capacitors for stability?

MC78L09ABD does not require output capacitance for stability, but a 0.33 µF input bypass capacitor is recommended-especially when the regulator is located far from the power supply filter or driving large capacitive loads. This capacitor improves high-frequency noise immunity and transient response. The datasheet confirms CO is optional but beneficial for dynamic load performance, while Cin is strongly advised for robust operation.

What is the thermal resistance (R_JA) of MC78L09ABD in SOIC-8 package?

MC78L09ABD in SOIC-8 (Case 751) has no fixed R_JA value-it varies with PCB copper area per Figure 8. With 3 mm × 3 mm copper pad, R_JA is approximately 170°C/W; with 10 mm × 10 mm, it drops to ~70°C/W. Unlike TO-92 (R_JA = 200°C/W), SOIC-8's internal lead-frame modification allows scalable thermal performance based on layout-enabling higher power dissipation without heatsinks.

Can MC78L09ABD be used as a current source?

Yes, MC78L09ABD can be configured as a constant-current source using external resistors, as shown in Figure 9 of the datasheet. By connecting the output to ground through a resistor and feeding feedback to the input, the regulator maintains fixed voltage across the resistor-yielding precise current (I_O = V_OUT/R). This mode leverages its internal reference and error amplifier, though power dissipation must remain within thermal limits.

Is MC78L09ABD pin-compatible with older 78L09 variants in TO-92?

No-MC78L09ABD uses an SOIC-8 package with 8 pins (including five GND terminals), whereas TO-92 versions (e.g., MC78L09ABPRAG) have only three pins (Output, Ground, Input) in a different physical layout. They share identical electrical functionality and output voltage but require PCB redesign for package substitution. Always verify footprint compatibility before replacement.