onsemi MC79L05ABD: Fixed -5V Linear Voltage Regulator Technical Overview

The onsemi MC79L05ABD is a fixed-output, negative voltage linear regulator belonging to the popular 79L series. Designed to deliver a precise -5V output at currents up to 100mA, this device is a fundamental component for providing stable, regulated power to low-power circuits, op-amp supplies, and as a secondary voltage reference in larger systems.

Housed in a compact SOT-89 surface-mount package, the regulator is engineered for space-constrained applications. Its internal design includes a thermal shutdown mechanism and short-circuit current limiting, which provide robust protection for both the IC itself and the downstream circuitry it powers. This makes it a reliable solution for a wide array of consumer and industrial electronic products.

A key characteristic of any linear regulator is its ability to reject noise and ripple from the input supply. The MC79L05ABD offers excellent ripple rejection, significantly attenuating unwanted AC components on the input DC line to ensure a clean, stable output voltage. For stable operation, it is recommended to use a small-value ceramic or tantalum capacitor on the input and output, typically 0.33 µF and 0.1 µF respectively, to improve transient response and stability.

While efficient and simple to use, designers must consider the device's power dissipation. As a linear regulator, it operates by dissipating excess power as heat. The voltage difference between the input and output (dropout voltage) multiplied by the output current determines the internal power dissipation. For reliable operation, ensuring that this dissipation remains within the limits set by the package's thermal characteristics is critical, especially when the input voltage is significantly higher than -5V.

ICGOOODFIND: The onsemi MC79L05ABD is a highly reliable, compact, and cost-effective solution for generating a precise -5V supply in low-current applications. Its built-in protection features and simple implementation make it an excellent choice for designers seeking to simplify power management in their negative voltage rail designs.

Keywords: Linear Regulator, Negative Voltage, -5V Output, SOT-89, Ripple Rejection