onsemi KSC5039H2

Overview

KSC5039H2 from Fairchild Semiconductor is an NPN silicon power transistor designed for high-voltage switching applications, featuring 800 V collector-base breakdown voltage (BVCBO), 400 V collector-emitter breakdown voltage (BVCEO), and 5 A DC collector current (IC) in a TO-220 package. It delivers 1.5 V collector-emitter saturation voltage at IC = 2.5 A / IB = 0.5 A and supports fast switching with 1 µs turn-on time, commonly used in flyback converters and horizontal deflection circuits.

For engineers reviewing the KSC5039H2 datasheet, pinout, applications, or equivalent options, key selection criteria include high-voltage blocking capability, safe operating area (SOA) robustness under pulse conditions, saturation voltage trade-offs at rated current, and thermal derating behavior above 25°C case temperature.

Technical Context

This device operates as a single NPN bipolar junction transistor optimized for high-voltage, medium-current switching-distinct from MOSFETs or IGBTs by its current-controlled base drive and inherent gain-dependent saturation behavior. Its SOA curve is defined up to 100 VCE at DC and extends to higher voltages under pulsed conditions (e.g., 50 µs, 100 µs, 1 ms).

Switching performance is characterized by tON = 1 µs, tSTG = 3 µs, and tF = 0.8 µs under standardized test conditions (VCC = 150 V, IC = 2.5 A, IB1 = –IB2 = 0.5 A, RL = 60 Ω), with fT = 10 MHz at VCE = 5 V and IC = 0.1 A, indicating usable bandwidth for kHz-range switching topologies.

Key Specifications

Pinout & Package

Package: TO-220 (3-lead, straight lead, insulated tab). Dimensions conform to JEDEC TO-220AB standard with mechanical outline provided in datasheet Rev. A (2000). Tab is electrically connected to collector.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar high-voltage NPN switching transistor applications.

Compared with MJD127G and BU508AF, the KSC5039H2 occupies a mid-tier niche: it offers superior voltage rating versus MJD127G while maintaining faster switching than BU508AF, making it optimal for 400 V-class CRT and industrial flyback designs where SOA and thermal stability are prioritized over extreme voltage margin or ultra-low conduction loss.

Availability

KSC5039H2 is available at Aetrix Electronics and suitable for horizontal deflection circuits, flyback converter primary switches, DC motor braking modules, and industrial inductive load drivers requiring stable component supply and long-term manufacturability.

Supply support for KSC5039H2 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 components before its acquisition by ON Semiconductor in 2016. Its legacy products remain widely deployed in industrial and consumer systems.

The KSC5039H2 belongs to Fairchild's high-voltage bipolar transistor product line, engineered specifically for reliability-critical horizontal deflection and flyback switching applications in CRT-based equipment and legacy industrial power supplies.

FAQ

What is the maximum safe collector-emitter voltage for KSC5039H2 in continuous operation?

The KSC5039H2 has a guaranteed BVCEO of 400 V at IC = 5 mA and IB = 0, verified per datasheet Rev. A. For continuous operation, VCEO must not exceed 400 V under any condition-including transients-to avoid avalanche breakdown. Derating is recommended for long-term reliability in high-temperature environments, and the SOA chart must be consulted for pulse conditions.

Does KSC5039H2 have an insulated tab, and how does that affect heatsink mounting?

Yes, the KSC5039H2 uses a TO-220 package with an insulated tab, meaning the metal tab (collector) is electrically isolated from the mounting surface. This allows direct attachment to a common heatsink without requiring insulating washers or pads, simplifying thermal management in multi-transistor layouts where collectors operate at different potentials.

What base drive current is required to fully saturate KSC5039H2 at 2.5 A collector current?

To achieve VCE(sat) ≤ 1.5 V at IC = 2.5 A, the KSC5039H2 requires IB = 0.5 A, as specified in the datasheet. This corresponds to a minimum hFE of 5 under saturation conditions. Base drive circuitry must deliver this peak current with low impedance to minimize switching delay and ensure consistent saturation across temperature and unit variation.

Can KSC5039H2 replace KSC5027Y in existing CRT deflection designs?

Yes, the KSC5039H2 is a direct functional upgrade to KSC5027Y, offering identical pinout, higher BVCEO (400 V vs. 300 V), and improved SOA at elevated VCE. No PCB changes are needed, but layout review is advised to confirm thermal margin given its 70 W PC rating and higher peak current capability.

Is KSC5039H2 compliant with RoHS or lead-free soldering requirements?

The KSC5039H2 was released in 2000 under Rev. A documentation and predates mandatory RoHS implementation. It is not certified RoHS-compliant; leaded solder processing applies. For new designs requiring RoHS, consult ON Semiconductor's modern equivalents such as the NSS12201LT1G, though electrical and thermal characteristics differ significantly.