onsemi KA79M12TU

Overview

KA79M12TU from Fairchild Semiconductor is a fixed-output, 3-terminal, medium-current negative voltage regulator delivering -12 V ±5% at up to 500 mA load current, with internal thermal overload protection, short-circuit current limiting, and safe-area compensation. It operates across an input range of -14.5 V to -30 V and is commonly used in dual-rail analog power supplies for op-amp circuits.

For engineers reviewing the KA79M12TU datasheet, pinout, applications, or equivalent options, key selection criteria include guaranteed -12 V output tolerance over temperature, dropout voltage ≤1.1 V at 500 mA, ripple rejection ≥54 dB at 120 Hz, and TO-220 package thermal resistance (R_θJC = 5 °C/W).

Technical Context

The KA79M12TU implements monolithic linear regulation using a PNP pass transistor with built-in current limiting and thermal shutdown circuitry. Its output voltage is internally trimmed and stabilized without external components, relying on internal bandgap reference and error amplifier feedback.

It requires only two external capacitors for stability: 0.33 µF at the input and 0.1 µF at the output (solid tantalum recommended). The device maintains regulation under line variations from -14.5 V to -30 V and load changes from 5 mA to 500 mA, with load regulation specified up to ±240 mV.

Key Specifications

Pinout & Package

KA79M12TU is supplied in a TO-220 package with three leads: Pin 1 (Ground), Pin 2 (Input), Pin 3 (Output). The metal tab is electrically connected to Pin 2 (Input) and must be isolated from chassis ground unless input is referenced to system ground.

Key Features

Applications

Equivalent & Alternatives

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

Compared with LM7912ACV and MC7912CT, the KA79M12TU offers superior thermal safety margin via integrated safe-area compensation and tighter load regulation (±240 mV vs ±300 mV), making it optimal for high-reliability industrial power rails where sustained 500 mA loads occur.

Availability

KA79M12TU is available at Aetrix Electronics and suitable for industrial power supplies, audio amplifier bias rails, and test & measurement equipment requiring stable component supply and long-term obsolescence management.

Supply support for KA79M12TU 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 specifically for cost-sensitive, medium-current negative voltage regulation in industrial and consumer electronics, emphasizing ruggedness, simplicity, and thermal resilience without external components.

FAQ

What is the maximum input voltage for KA79M12TU?

The KA79M12TU supports a maximum input voltage of -30 V when regulating -12 V output. Absolute maximum rating is -35 V for VO = -5 V to -18 V variants, but per Electrical Characteristics table on page 5, KA79M12 is rated for VI = -14.5 V to -30 V, with absolute limit of -35 V confirmed in Absolute Maximum Ratings. Exceeding -30 V risks violating safe operating area under load.

Does KA79M12TU require external capacitors?

Yes - KA79M12TU requires a 0.33 µF input capacitor (solid tantalum preferred) and a 0.1 µF output capacitor (ceramic or tantalum) for stability and transient response. These are mandatory per the datasheet's Typical Applications section and Schematic Diagram; omission may cause oscillation or poor ripple rejection.

Is KA79M12TU pin-compatible with LM7912?

No - KA79M12TU and LM7912 share identical pinout (GND-IN-OUT in TO-220), but KA79M12TU has different internal safe-area compensation and tighter load regulation (±240 mV vs ±300 mV for LM7912). While physically interchangeable, performance differences affect thermal margin and precision in high-stress applications.

What is the thermal resistance of KA79M12TU?

The KA79M12TU has a junction-to-case thermal resistance (R_θJC) of 5 °C/W, measured from die to the TO-220 metal tab. This value assumes proper mechanical mounting with thermal compound and adequate heatsinking; junction-to-ambient (R_θJA) is 65 °C/W without heatsink.

Can KA79M12TU be used in automotive applications?

KA79M12TU is rated for 0 °C to +125 °C operation and lacks AEC-Q100 qualification. While functional in cabin-mounted systems, it is not recommended for under-hood use. For automotive-grade alternatives, consider MC7912CT (–40 °C to +125 °C) or ON Semiconductor's newer NCV7912 series, both explicitly qualified for automotive environments.