onsemi KA79M12

Overview

KA79M12 from Fairchild Semiconductor is a fixed-output, 3-terminal negative voltage regulator delivering −12 V at up to 500 mA output current in TO-220 package. It features internal thermal overload protection, short-circuit current limiting, safe-area compensation, and operates across 0 °C to +125 °C junction temperature range. It is used in industrial power supplies requiring stable negative bias for op-amps, analog circuitry, and legacy logic systems.

For engineers reviewing the KA79M12 datasheet, pinout, applications, or equivalent options, key selection criteria include guaranteed −12 V output tolerance (±2.5% at 25 °C), dropout voltage ≤1.1 V at 500 mA, ripple rejection ≥60 dB at 120 Hz, and thermal resistance of 5 °C/W (junction-to-case).

Technical Context

The KA79M12 is a monolithic linear regulator implementing series-pass transistor control with built-in current limiting and thermal shutdown. Its regulation architecture relies on internal bandgap reference and error amplifier feedback to maintain output stability under varying load and line conditions.

It requires no external components for basic operation but benefits from input (0.33 µF) and output (0.1 µF solid tantalum) capacitors for stability and transient response. Ripple rejection and noise performance are specified at 120 Hz and over 10 Hz–100 kHz bandwidth respectively.

Key Specifications

Pinout & Package

KA79M12 is supplied in TO-220 package with three leads: Pin 1 = Ground, Pin 2 = Input (negative supply), Pin 3 = Output (regulated −12 V). The metal tab is electrically connected to Pin 2 (Input) and serves as primary thermal path.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar negative voltage regulator applications.

Compared with LM7912CDT and MC79M12BDTG, the KA79M12 offers superior ripple rejection (60 dB vs. 54–57 dB), tighter output tolerance (±2.5% vs. ±3%), and lower dropout (1.1 V vs. 1.3 V), making it preferable for noise-sensitive analog rails and thermally constrained layouts.

Availability

KA79M12 is available at Aetrix Electronics and suitable for industrial analog signal conditioning, legacy logic biasing, and embedded control system power management requiring stable component supply and long-term obsolescence resilience.

Supply support for KA79M12 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

Fairchild Semiconductor was a U.S.-based semiconductor company specializing in power management, analog, and discrete devices before its acquisition by ON Semiconductor in 2016.

The KA79MXX series was designed as a robust, drop-in replacement family for legacy 79xx negative regulators, emphasizing thermal survivability, short-circuit resilience, and minimal external component count in industrial power conversion.

FAQ

What is the maximum input voltage rating for KA79M12?

The KA79M12 has an absolute maximum input voltage of −40 V for the −24 V output variant, but for the KA79M12 specifically, the datasheet specifies −30 V as the maximum input voltage under normal operating conditions (VI = −14.5 V to −30 V). Exceeding −30 V risks permanent damage even with thermal protection active, as internal junction breakdown may occur before thermal shutdown triggers.

Does KA79M12 require input and output capacitors to operate stably?

Yes, the KA79M12 requires a 0.33 µF solid tantalum capacitor at the input and a 0.1 µF solid tantalum capacitor at the output for guaranteed stability per the datasheet test circuit. Aluminum electrolytic substitutes (e.g., 25 µF) are permitted at the input, but output capacitance must remain ≤0.1 µF to avoid oscillation - exceeding this value degrades phase margin and may cause instability.

Can KA79M12 be used in surface-mount designs?

No, the standard KA79M12 is offered only in through-hole TO-220 package. While Fairchild also produced a D-PAK variant (KA79M12R), that part is explicitly designated with the "R" suffix and has different mechanical dimensions and thermal characteristics. Using KA79M12 in SMT assembly would require custom adapter or rework and is not supported by the manufacturer's qualification or reliability data.

What is the typical output voltage drift over temperature for KA79M12?

The KA79M12 exhibits a typical output voltage drift of −0.8 mV/°C (ΔVO/ΔT) at IO = 5 mA, meaning its output decreases by approximately 0.8 mV for every 1 °C rise in junction temperature. Over the full 0 °C to +125 °C operating range, this results in a total drift of about −100 mV - well within the ±2.5% (±300 mV) initial tolerance band, ensuring system-level compliance.

Is KA79M12 pin-compatible with LM7912?

Yes, KA79M12 is pin-compatible with LM7912 in TO-220 package: Pin 1 = Ground, Pin 2 = Input, Pin 3 = Output. Both share identical pinout, terminal functions, and mechanical footprint. However, differences in quiescent current, ripple rejection, and thermal resistance mean electrical behavior under stress conditions (e.g., high ripple, elevated ambient) may vary - validation in the target application is recommended.