onsemi KA78R33CYDTU

Overview

KA78R33CYDTU from ON Semiconductor is a 1A, 3.3V fixed-output low-dropout linear voltage regulator in TO-220F-4L package with output disable control, thermal shutdown, and overcurrent protection. It delivers stable 3.3V power for microcontroller core supplies, industrial I/O modules, and embedded sensor interfaces where input-to-output differential voltage is constrained.

For engineers reviewing the KA78R33CYDTU datasheet, pinout, applications, or equivalent options, key selection criteria include dropout voltage ≤0.5V at 1A, disable function threshold (V_disH ≥2.0V), ±2.4% output voltage tolerance, and thermal resistance R_θJC = 4.31°C/W for heatsink-integrated designs.

Technical Context

The KA78R33CYDTU integrates bandgap reference, error amplifier, pass transistor, and protection circuitry-including SOA-limited peak current sensing, thermal shutdown latch, and overvoltage clamp-within a monolithic silicon die. Its disable function operates via TTL-compatible logic-level control on Pin 4 (V_dis), enabling system-level power sequencing without external MOSFETs.

Designed for operation across -20°C to +80°C ambient, it maintains regulation with input voltages from 4.0V to 10.0V and supports up to 15W power dissipation when mounted on an adequate heatsink. Ripple rejection exceeds 45dB at 120Hz, making it suitable for post-regulation of switched-mode supply outputs.

Key Specifications

Pinout & Package

KA78R33CYDTU uses the TO-220F-4L full-mold plastic package with exposed tab (electrically connected to Pin 3/GND), optimized for vertical mounting and heatsink attachment.

Key Features

Applications

Equivalent & Alternatives

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

Compared with LM2936MP-3.3/NOPB, KA78R33CYDTU supports full 1A load with lower dropout but higher quiescent current; compared with TPS7A4700RGWR, it offers simpler implementation and built-in disable/thermal protection at the cost of higher output noise and fixed voltage.

Availability

KA78R33CYDTU is available at Aetrix Electronics and suitable for industrial automation, embedded computing, and medical device applications requiring stable component supply, long-term lifecycle support, and traceable sourcing.

Supply support for KA78R33CYDTU 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 is a global semiconductor manufacturer specializing in energy-efficient power management, analog, sensor, and connectivity solutions for automotive, industrial, and cloud infrastructure markets.

The KA78RXXC series was developed to replace legacy 78xx regulators with enhanced dropout performance, integrated disable functionality, and robust protection-targeting industrial control, test equipment, and embedded systems demanding reliability under variable load and thermal conditions.

FAQ

What is the maximum input voltage rating for KA78R33CYDTU?

The absolute maximum input voltage for KA78R33CYDTU is 35V, but its recommended operating range is 4.0V to 10.0V for optimal regulation and thermal performance. Exceeding 10.0V increases power dissipation significantly and may trigger thermal shutdown under full load. Always verify input transient conditions against this limit in your design.

Does KA78R33CYDTU require an input capacitor?

Yes, KA78R33CYDTU requires an input capacitor (Ci) if located more than a few centimeters from the main power supply filter, as stated in the typical application circuit. A minimum 10μF low-ESR ceramic capacitor placed close to Pin 1 (Vin) improves high-frequency stability and reduces line-transient susceptibility. Omitting Ci may cause oscillation or poor transient response.

Can KA78R33CYDTU be used without a heatsink?

KA78R33CYDTU can operate without a heatsink only at reduced load currents: its no-heatsink power dissipation limit is 1.5W. At 1A output and 5V input (2.7W dissipation), a heatsink is mandatory. Use the junction-to-case thermal resistance (4.31°C/W) and your heatsink's thermal resistance to calculate actual junction temperature and ensure it remains below 150°C.

How does the disable function behave during power-up?

KA78R33CYDTU powers up enabled by default: the output activates when Vin reaches regulation threshold, provided Vdis is left floating or pulled above 2.0V. To ensure controlled startup, tie Pin 4 (Vdis) to Vin through a pull-up resistor or drive it actively. Floating Vdis may result in unpredictable enable timing due to internal leakage paths.

Is KA78R33CYDTU RoHS compliant and halogen-free?

Yes, KA78R33CYDTU is RoHS compliant and halogen-free per ON Semiconductor's product compliance documentation. The TO-220F-4L package meets JEDEC standards for lead-free soldering (reflow profile up to 260°C), and material declarations confirm absence of brominated flame retardants and chlorine-based compounds.