onsemi KA7818ETSTU

Overview

KA7818ETSTU from ON Semiconductor is a fixed-output +18 V, 1 A positive linear voltage regulator in TO-220 (dual-gauge) package, featuring thermal overload protection, short-circuit protection, and safe operating area (SOA) protection. It delivers stable DC power for industrial control logic, analog sensor interfaces, and legacy embedded systems requiring robust, low-noise 18 V supply rails.

For engineers reviewing the KA7818ETSTU datasheet, pinout, applications, or equivalent options, this page provides verified electrical specs, thermal performance data, real-world use cases, and validated alternative parts - all aligned with Fairchild/ON Semiconductor's KA78XXE family documentation (Rev. 1.9, April 2015).

Technical Context

The KA7818ETSTU implements a classic three-terminal series pass architecture with internal error amplifier, reference voltage generator, current-limiting circuitry, thermal shutdown comparator, and SOA protection. Its regulation loop maintains output stability under load transients up to 1.5 A peak and input variations from 21 V to 33 V.

It operates across –40°C to +125°C junction temperature range with guaranteed ±4% output voltage tolerance at 25°C and includes built-in ripple rejection (53–69 dB at 120 Hz), low output noise (110 μV RMS, 10 Hz–100 kHz), and 2 V dropout voltage at 1 A load.

Key Specifications

Pinout & Package

KA7818ETSTU uses the standard TO-220 (dual-gauge) package with metal tab electrically connected to Pin 2 (GND). Mounting requires isolation washer if heatsink is grounded.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar positive linear regulator applications.

Compared with KA7818ETSTU, LM7818CD2T offers tighter initial accuracy but higher static power draw, while MC7818CD2TR4 improves dynamic regulation and ESD immunity - both require no PCB changes but differ in thermal and noise performance trade-offs.

Availability

KA7818ETSTU is available at Aetrix Electronics and suitable for industrial control power, analog sensor conditioning, legacy embedded system rail replacement, and motor driver bias supply applications requiring stable component supply and long-term manufacturability.

Supply support for KA7818ETSTU 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

ON Semiconductor (formerly Fairchild Semiconductor) is a global semiconductor supplier specializing in power management, analog, and discrete devices for automotive, industrial, and cloud infrastructure markets.

The KA78XXE series was designed as a drop-in, industry-standard replacement for legacy 78xx linear regulators - optimized for cost-sensitive, high-reliability applications where simplicity, thermal robustness, and proven topology matter more than ultra-low IQ or adjustable output.

FAQ

What is the maximum input voltage for KA7818ETSTU?

The absolute maximum input voltage for KA7818ETSTU is 40 V when VO = 24 V, but its recommended operating range is 21 V to 33 V for reliable 18 V regulation. Exceeding 33 V risks excessive power dissipation and thermal shutdown, especially at full 1 A load. Always verify input ripple and transient peaks stay within this window.

Does KA7818ETSTU require external capacitors?

Yes, KA7818ETSTU requires a minimum 0.33 μF ceramic capacitor on the input and 0.1 μF ceramic capacitor on the output, placed as close as possible to the device pins. These stabilize the internal control loop and suppress high-frequency noise; omitting them may cause oscillation or poor transient response.

Is KA7818ETSTU pin-compatible with other 78xx-series regulators?

Yes, KA7818ETSTU uses the standard three-terminal TO-220 pinout (Input–GND–Output) and is mechanically and electrically pin-compatible with industry-standard 7818 regulators including LM7818 and MC7818 - enabling direct replacement without layout modification.

What thermal management is needed for KA7818ETSTU at 1 A load?

At 1 A and 33 V input, KA7818ETSTU dissipates up to 15 W (P_D = (33 V − 18 V) × 1 A). With R_θJC = 5 °C/W, junction temperature rise above case is ~75°C. A heatsink with ≤10 °C/W total thermal resistance (including interface) is recommended to keep T_J ≤125°C in 70°C ambient.

Can KA7818ETSTU be used in adjustable configurations?

While KA7818ETSTU is a fixed +18 V device, it can be adapted for adjustable output using external resistive feedback networks per Fairchild AN-113 - though this compromises accuracy, line/load regulation, and thermal stability. For true adjustability, consider LM317 or ON Semiconductor's NCV317 instead.