onsemi KA7905TU

Overview

KA7905TU from ON Semiconductor is a fixed-output, three-terminal negative voltage regulator delivering −5 V at up to 1 A output current with ±4% output voltage tolerance, internal thermal overload and short-circuit protection, and 2 V dropout voltage at 1 A - used in industrial power supplies, dual-rail analog circuits, and legacy embedded systems requiring stable negative bias.

For engineers reviewing the KA7905TU datasheet, pinout, applications, or equivalent options, this page provides verified electrical specifications, TO-220 package layout, real-world load/line regulation behavior, thermal resistance data (R_θJC = 5°C/W), and validated alternative parts for negative rail design continuity.

Technical Context

The KA7905TU implements a monolithic PNP pass transistor architecture with built-in current limiting, thermal shutdown, and safe operating area (SOA) compensation - enabling robust operation under sustained overload or ambient temperature extremes from 0°C to +125°C. It requires no external components for basic regulation but benefits from input (2.2 μF solid tantalum) and output (1 μF) capacitors for stability and transient response.

Unlike low-dropout regulators, the KA7905TU operates with a minimum 2 V input-to-output differential (dropout) and delivers ripple rejection of 54–60 dB at 120 Hz - making it suitable for post-filter regulation in transformer-based AC/DC supplies rather than battery-powered or ultra-low-voltage systems.

Key Specifications

Pinout & Package

KA7905TU is housed in a TO-220 (dual-gauge) thermally enhanced plastic package with exposed metal tab electrically connected to Pin 2 (Input). The package meets JEDEC standard MO-002AB and supports vertical mounting with mechanical screw-down heatsinking.

Key Features

Applications

Equivalent & Alternatives

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

Compared with LM7905CT and KA7905T, the KA7905TU offers identical regulation performance but superior mechanical robustness via dual-gauge TO-220 construction - critical for high-vibration industrial enclosures and long-term thermal cycling reliability.

Availability

KA7905TU is available at Aetrix Electronics and suitable for industrial power supplies, analog signal conditioning circuits, and legacy embedded system repairs requiring stable component supply and long-term lifecycle support.

Supply support for KA7905TU 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 supplier of energy-efficient semiconductor solutions, specializing in power management, analog, and discrete devices for industrial, automotive, and cloud infrastructure markets.

The KA79XX series belongs to ON Semiconductor's legacy linear regulator product line, designed specifically for cost-sensitive, high-reliability negative rail generation in transformer-based power supplies and analog subsystems.

FAQ

What is the maximum input voltage rating for KA7905TU?

The KA7905TU has an absolute maximum input voltage of −35 V. Operation above this level risks permanent damage to the internal pass transistor. For reliable −5 V output, the recommended input range is −7 V to −20 V - ensuring adequate dropout margin while minimizing power dissipation and thermal stress. Always verify input transient suppression in your design to prevent accidental violation of this rating.

Does KA7905TU require external capacitors to operate stably?

Yes, KA7905TU requires a 2.2 μF solid tantalum capacitor at the input (CI) and a 1 μF capacitor at the output (CO) for guaranteed stability and optimal transient response, as specified in the datasheet Figure 7. Aluminum electrolytic capacitors may be used for CO only if capacitance is increased ≥10× (≥10 μF); omitting either capacitor risks oscillation or poor load step recovery.

Can KA7905TU be used in parallel to increase output current?

No, KA7905TU is not designed for parallel operation. Its output voltage tolerance (±4%) and lack of current-sharing features mean unequal current division will occur - potentially causing one device to dominate conduction and overheat. For >1 A requirements, use a higher-current regulator (e.g., KA79L05 for 100 mA or discrete pass transistor augmentation) instead of paralleling KA7905TU units.

Is KA7905TU pin-compatible with LM7905CT?

Yes, KA7905TU is fully pin-compatible with LM7905CT: both use TO-220 packages with identical 1-GND / 2-Input / 3-Output pinout and share identical electrical characteristics including −5 V output, ±4% tolerance, and 1 A current capability. This allows direct substitution in existing designs without PCB modification.

What thermal management is required for KA7905TU at full 1 A load?

At 1 A output with −7 V input (2 V dropout), KA7905TU dissipates 2 W. With R_θJC = 5°C/W and typical R_θCS ≈ 1°C/W (mica washer + thermal paste), a heatsink with R_θSA ≤ 14°C/W is required to maintain T_J ≤ 125°C at 25°C ambient. Without a heatsink, power must be limited to ~2.3 W - corresponding to ~0.9 A at −7 V input or lower current at higher input differentials.