LM78XX Series 3-Terminal 1A Positive Voltage Regulators

Category: Electronics, Fairchild Semiconductor, Regulators

Introduction & Features

The LM78XX series, also known as KA78XX and MC78XX, is a family of 3-terminal positive voltage regulators available in TO-220 and D-PAK packages. These fixed voltage regulators offer output voltages in multiple standard values such as 5V, 6V, 8V, 9V, 10V, 11V, 12V, 15V, 18V, and 24V, catering to a broad spectrum of applications. The device series is highly robust, featuring internal current limiting, thermal shutdown, and safe area protection which render the components essentially indestructible under normal operation. The devices are capable of providing up to 1A of output current if they are properly heat-sinked. While they are primarily designed as fixed voltage regulators, they can also be adapted for adjustable voltage and current outputs with the addition of external components.

Protection & Reliability

The LM78XX series is engineered with reliability in mind, incorporating protective features that include thermal overload protection and short circuit protection. It also includes Output Transistor Safe Operating Area (SOA) Protection, ensuring long-term reliability.

Ordering Information & Options

The devices come in various versions, differing by output voltage, package type, operating temperature tolerances, and precision:
KA78XXCT series operates within 0 to +125°C with a tolerance margin of 4%,
KA78XXAT comes in a TO-220 package,
KA78XXIT and KA78XXAR series provides a higher precision with a tolerance margin of 2% in D-PAK packaging, and
KA78XXR and KA78XXIR series also operate within the same temperature range. These variants cater to various requirements of precision, packaging, and thermal performance for diverse applications.

Block Diagram & Internal Circuitry

The block diagram presented in the datasheet illustrates the internal circuitry of the LM78XX series. It includes a series pass element, current generator, short-circuit (SC) protection, starting circuit, reference voltage, error amplifier, and thermal protection connected to the three terminals identified as Input, Ground (GND), and Output. This diagram showcases the comprehensive regulation and protection mechanisms designed to maintain stable voltage output and safeguard the device.

Note: The datasheet content is authored by Fairchild Semiconductor as per the revision history indicating “Rev. B.” However, it should be highlighted that the actual datasheet may contain further information including detailed specifications, application notes, and additional data pertinent to the LM78XX series regulators, which requires a thorough review beyond the first two pages for complete understanding and application.