onsemi KA78R08CTU

Overview

KA78R08CTU from ON Semiconductor is a 1A, 8V fixed-output low-dropout linear voltage regulator in TO-220F-4L package with output disable control, thermal shutdown, and overcurrent protection. It delivers stable 8V power at up to 1A load with ≤0.5V dropout at full current, supporting industrial power rails where input-to-output differential is constrained. Used in embedded control modules requiring regulated 8V supply with enable/disable sequencing.

For engineers reviewing the KA78R08CTU datasheet, pinout, applications, or equivalent options, key selection criteria include its 8V ±2% output tolerance, 1A continuous output capability, disable pin logic (active-high enable), thermal shutdown threshold (~150°C), and TO-220F-4L mechanical footprint compatibility with heatsink mounting.

Technical Context

The KA78R08CTU integrates bandgap reference, error amplifier, pass transistor, and protection circuitry in a monolithic IC. Its internal architecture includes SOA-limited peak current protection, overvoltage clamping on the output, and a dedicated V_DIS terminal that controls output state via TTL-compatible logic thresholds (V_DISH ≥ 2.0V, V_DISL ≤ 0.8V).

It operates across -20°C to +80°C ambient temperature with junction-to-case thermal resistance of 4.31°C/W, enabling 15W power dissipation with heatsink. Input voltage range is 9V to 25V per specification, ensuring reliable regulation under typical 12V/24V system rails with ripple and transients.

Key Specifications

Pinout & Package

KA78R08CTU uses the TO-220F-4L full-mold package with exposed tab (electrically connected to GND), optimized for vertical heatsink mounting and high thermal reliability in industrial enclosures.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar fixed-output LDO regulator applications.

Compared with LM2940CT-8.0 and TLV76780QWDRBRQ1, the KA78R08CTU uniquely combines TO-220F-4L mechanical robustness, hardware disable control, and 0.5V dropout in a cost-optimized industrial-grade part-making it optimal for legacy-compatible, heatsink-mounted 8V power stages where pin count and thermal mass matter more than miniaturization.

Availability

KA78R08CTU is available at Aetrix Electronics and suitable for industrial PLCs, automotive body control units, medical sensor hubs, and point-of-sale terminals requiring stable component supply with long-term manufacturability and thermal resilience.

Supply support for KA78R08CTU 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 focused on energy-efficient electronics, with leadership in power management, analog, and sensor technologies.

The KA78RXXC series was designed for industrial and automotive power regulation applications demanding ruggedized packaging, integrated protection, and simple fixed-output LDO functionality without complex external components.

FAQ

What is the minimum input voltage required for KA78R08CTU to regulate 8V output?

The KA78R08CTU requires a minimum input voltage of 9V to maintain regulation at full 1A load, based on its maximum 0.5V dropout specification. At lighter loads, regulation may sustain down to ~8.3V input, but design margin should retain ≥9V to ensure stability across temperature and line variations. The KA78R08CTU datasheet specifies Vin = 9V to 25V for guaranteed performance.

Does KA78R08CTU require an output capacitor, and what value is recommended?

Yes, KA78R08CTU requires an output capacitor for stability and transient response. The datasheet specifies Co > 47μF - a low-ESR electrolytic or polymer capacitor rated ≥16V is recommended. Smaller values risk oscillation under dynamic load steps; ceramic capacitors alone are insufficient due to insufficient ESR. The KA78R08CTU application circuit confirms this requirement in Figure 1.

How does the disable function of KA78R08CTU behave electrically when disabled?

When the V_DIS pin is pulled ≤0.8V (logic low), the KA78R08CTU disables its output stage, placing Vo in high-impedance state with leakage current <100μA. Input current drops to ≤20μA, and the pass transistor is fully turned off. This behavior is confirmed in the Electrical Characteristics table under "Disable bias current low" and functional description. The KA78R08CTU does not sink or source significant current at Vo during disable.

Can KA78R08CTU be used without a heatsink?

KA78R08CTU can operate without a heatsink only at very low power dissipation: maximum 1.5W (Pd1) at ambient ≤80°C. At 1A load with 5V input-to-output differential (e.g., 13V in → 8V out), power dissipation is 5W - exceeding the no-heatsink limit. Therefore, a heatsink is mandatory for full-load operation. Thermal resistance data (Rθjc = 4.31°C/W) confirms heatsink dependency; the KA78R08CTU absolute maximum ratings explicitly define Pd2 = 15W only "with heatsink".

Is KA78R08CTU pin-compatible with other regulators in the KA78RXXC family?

Yes, all KA78RXXC-series parts including KA78R08CTU share identical TO-220F-4L pinout (Vin, Vo, GND, Vdis) and electrical interface. Output voltage is the only variant parameter - KA78R05CTU (5V), KA78R12CTU (12V), etc. - enabling drop-in replacement across voltages in same PCB footprint. This compatibility is documented in the Ordering Information table and Mechanical Dimensions section for KA78RXXC-SERIES.