onsemi KSC2518R

Overview

KSC2518R from Fairchild Semiconductor is an NPN epitaxial silicon transistor designed for high-voltage, high-speed switching in inductive load applications such as SMPS and motor control. It supports 400 V V_CEO, 4 A DC collector current, 1 V V_CE(sat) at 1.5 A/0.3 A drive, and operates up to 150 °C junction temperature.

For engineers reviewing the KSC2518R datasheet, pinout, applications, or equivalent options, key selection criteria include reverse-biased SOA validation under clamped inductive switching, pulse-rated collector current (8 A), and TO-220 package thermal performance with 40 W dissipation at T_C = 25 °C.

Technical Context

The KSC2518R is optimized for fast-switching, high-voltage power conversion where robust safe operating area (SOA) under reverse bias is critical. It features specified V_CEX(sus) ratings of 450 V (clamped, 125 °C) and 400 V (clamped, 125 °C), validated with 180 µH inductance and active base drive control.

Its switching timing-t_ON = 1 µs, t_STG = 2.5 µs, t_F = 0.7 µs-is characterized at V_CC = 150 V, I_C = 2 A, R_L = 75 Ω, and symmetrical ±0.4 A base drive, confirming suitability for hard-switched converters operating below 100 kHz.

Key Specifications

Pinout & Package

Package: TO-220 (3-lead, straight lead, insulated tab). Dimensions per Fairchild Rev. A: 15.90 mm × 10.08 mm × 18.95 mm max height; mounting hole ø3.60 mm; lead pitch 2.54 mm.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MJD253 and BU508A, the KSC2518R uniquely provides factory-characterized reverse-biased SOA at elevated temperature and inductive load conditions-enabling deterministic design of clamped snubber circuits without empirical testing.

Availability

KSC2518R is available at Aetrix Electronics and suitable for switch-mode power supplies, industrial motor drives, and high-voltage relay drivers requiring stable component supply and long-term industrial lifecycle support.

Supply support for KSC2518R 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 discrete and analog ICs, acquired by ON Semiconductor in 2016.

The KSC2518R belongs to Fairchild's high-voltage bipolar transistor product line, engineered specifically for ruggedized switching in industrial power conversion where SOA integrity under transient inductive stress is non-negotiable.

FAQ

What is the maximum continuous collector current rating for the KSC2518R?

The KSC2518R has a DC collector current rating of 4 A at case temperature T_C = 25 °C. This rating assumes adequate heatsinking; derating is required above 25 °C per the published power derating curve. At T_C = 100 °C, the usable I_C drops to approximately 2.2 A. The KSC2518R also supports 8 A pulsed collector current under specified pulse conditions (PW ≤ 350 µs, duty cycle ≤ 10%).

Does the KSC2518R support reverse-biased safe operating area (RBSOA) operation?

Yes-the KSC2518R is explicitly characterized for reverse-biased SOA. Its V_CEX(sus) is specified at 450 V (IC = 2 A, IB1 = –IB2 = 0.4 A, T_a = 125 °C, L = 180 µH, clamped) and 400 V (IC = 4 A, IB1 = 0.8 A, –IB2 = 0.4 A, same conditions). These values appear in the official Fairchild datasheet and confirm its suitability for actively clamped inductive switching. The KSC2518R is one of few discrete transistors with factory-tested RBSOA data.

What is the pin configuration of the KSC2518R in its TO-220 package?

The KSC2518R uses a standard TO-220 package with 3 leads and insulated tab. Pin 1 is Base, Pin 2 is Collector, and Pin 3 is Emitter-viewed from the front (flat side) with leads pointing downward. This configuration is confirmed in the "Package Dimensions" drawing and "1.Base 2.Collector 3.Emitter" note in the Fairchild KSC2518 datasheet Rev. A. Mounting orientation must ensure electrical isolation between the collector (tab) and heatsink unless using insulating hardware.

How does the KSC2518R's hFE classification 'R' affect base drive design?

The 'R' suffix denotes hFE1 = 20–40 at V_CE = 5 V and I_C = 0.3 A. For reliable saturation at full 4 A load, designers should size base drive to deliver ≥0.3 A (for 1.5 A I_C) or ≥0.8 A (for 4 A I_C), assuming minimum hFE = 20. The KSC2518R's consistent hFE band simplifies gate/base driver selection and avoids overdesign seen with wider-gain transistors. This hFE range is explicitly defined in the datasheet's "hFE Classification" table.

Can the KSC2518R replace the KSC2518 without modification?

Yes-the KSC2518R is a hFE-binned version of the base KSC2518, sharing identical absolute maximum ratings, electrical characteristics, package, pinout, and SOA specifications. The 'R' denotes the 20–40 hFE1 range; other variants (O = 30–60, Y = 40–80) differ only in gain distribution. No PCB or schematic changes are needed when substituting KSC2518R for KSC2518, provided the circuit functions within the R-bin's gain window. All KSC2518R units meet the full KSC2518 datasheet.