onsemi KA79M05

Overview

KA79M05 from Fairchild Semiconductor is a fixed-output, 3-terminal, medium-current negative voltage regulator delivering -5 V at up to 500 mA. It features internal thermal overload protection, short-circuit current limiting, and safe-area compensation in a TO-220 package. It is used in industrial power supplies requiring stable, low-noise negative rail generation.

For engineers reviewing the KA79M05 datasheet, pinout, applications, or equivalent options, this page provides verified electrical specs, thermal characteristics, real-world use cases, and validated alternative parts for design-in and BOM optimization.

Technical Context

The KA79M05 operates as a monolithic linear regulator with no external components required for basic functionality. Its architecture integrates current limiting, thermal shutdown, and output transistor safe-area compensation - enabling robust operation under overload and fault conditions without external circuitry.

It maintains regulation across input voltages from -7 V to -25 V while delivering stable -5 V output over load currents from 5 mA to 500 mA. Ripple rejection of 54–60 dB at 120 Hz and dropout voltage of 1.1 V at 500 mA define its performance envelope in noisy or margin-constrained supply environments.

Key Specifications

Pinout & Package

KA79M05 is housed in a TO-220 package with three leads: Pin 1 (GND), Pin 2 (Input), Pin 3 (Output). The metal tab is electrically connected to Pin 2 (Input) and serves as the primary thermal path.

Key Features

Applications

Equivalent & Alternatives

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

Compared with LM79M05 and KA79M05R, the KA79M05 offers identical regulation performance and protection features in a through-hole TO-220 package optimized for manual prototyping and heatsink-integrated industrial designs - making it ideal for applications where mechanical robustness and thermal interface control are critical.

Availability

KA79M05 is available at Aetrix Electronics and suitable for industrial power supplies, analog signal conditioning, test equipment, and legacy digital logic support requiring stable component supply and long-lifecycle availability.

Supply support for KA79M05 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 instrumentation applications - emphasizing ruggedness, simplicity, and thermal resilience without external components.

FAQ

What is the maximum input voltage for KA79M05?

The KA79M05 supports a maximum input voltage of -35 V for output voltages between -5 V and -18 V. This rating ensures safe operation with transformer-derived unregulated supplies that may exhibit significant ripple or transient overshoot. Exceeding -35 V risks permanent damage to the internal pass transistor, regardless of load or thermal conditions. Always verify input voltage margins using worst-case AC line and load-dump simulations before finalizing the design.

Does KA79M05 require external capacitors to operate stably?

Yes, KA79M05 requires two external capacitors for stable operation: a 0.33 µF solid tantalum capacitor (C_I) at the input and a 0.1 µF ceramic capacitor (C_O) at the output. These values are specified in the datasheet test circuit and are mandatory for phase margin and transient response compliance. Substituting aluminum electrolytic for C_I is permitted only at 25 µF minimum, but tantalum is preferred for ESR stability. Increasing C_O beyond 0.1 µF may cause oscillation.

What is the thermal resistance of KA79M05 in TO-220 package?

The KA79M05 in TO-220 package has a junction-to-case thermal resistance (θ_JC) of 5 °C/W, measured from die to the metal tab. Its junction-to-ambient resistance (θ_JA) is 65 °C/W with no heatsink. When mounted to a 10 cm² aluminum heatsink with thermal grease, typical θ_JA drops to ~25 °C/W, enabling full 500 mA output at ambient temperatures up to +70 °C. Always verify actual junction temperature using T_J = T_A + P_D × θ_JA.

Can KA79M05 be used in place of LM79M05?

Yes, KA79M05 is functionally and pin-compatible with LM79M05 across all electrical parameters, including output voltage tolerance, dropout, ripple rejection, and protection features. Both share identical TO-220 pinout (GND–Input–Output), thermal specs, and application circuits. No PCB changes are required for substitution. However, LM79M05 may offer extended temperature variants (-40 °C to +125 °C), whereas KA79M05 is rated for 0 °C to +125 °C per ordering information.

What protection features does KA79M05 include?

KA79M05 integrates three key protection mechanisms: internal thermal overload shutdown (activates at ~125 °C junction temperature), short-circuit current limiting (~140 mA peak), and safe-area compensation for the output transistor. These functions operate autonomously without external components. Thermal shutdown is non-latching and recovers automatically once cooled. Short-circuit current limit prevents destructive failure during output faults, and safe-area compensation avoids secondary breakdown during transient overloads - collectively making KA79M05 "essentially indestructible" per its original datasheet description.