onsemi KSE5742

Overview

KSE5742 from Fairchild Semiconductor is an NPN silicon Darlington transistor designed for high-voltage power switching in inductive circuits, featuring a 400 V collector-emitter sustaining voltage (BV_CEO(sus)), 8 A DC collector current rating, and 80 W collector dissipation at T_C = 25°C - used in motor control, solenoid drivers, and inverters.

For engineers reviewing the KSE5742 datasheet, pinout, applications, or equivalent options, key selection criteria include its TO-220 package, 800 V V_CEV, 2.5–3.5 V V_BE(sat) across 4–8 A, safe operating area (SOA) compliance up to 250 V/6 A, and Darlington gain (h_FE = 200–400 at I_C = 4 A).

Technical Context

The KSE5742 integrates two cascaded NPN transistors in a monolithic Darlington configuration, enabling high current gain with low base drive requirements. It supports fast switching in inductive loads with t_D = 0.04 µs, t_R = 0.5 µs, t_S = 8 µs, and t_F = 2 µs under V_CC = 250 V, I_C(pk) = 6 A conditions.

Its reverse-bias safe operating area (RBSOA) and forward-biased SOA are characterized up to 100 µs pulse width, supporting robust operation in relay/solenoid snubberless switching and flyback energy recovery. The integrated emitter-base diode (V_F = 2.5 V at I_F = 5 A) provides inherent clamping capability.

Key Specifications

Pinout & Package

Package: TO-220 (3-lead, straight lead, insulated tab). Dimensions per Fairchild Rev. A1: 15.90 mm × 10.08 mm × 18.95 mm max, with mounting hole Ø3.60 mm.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MJD5742 and BDW93C, the KSE5742 uniquely balances 400 V/800 V voltage ratings, 8 A current capability, and 80 W dissipation in a through-hole TO-220 package - making it irreplaceable in legacy 100–400 V inductive switching designs requiring proven thermal margin and mechanical robustness.

Availability

KSE5742 is available at Aetrix Electronics and suitable for motor control, solenoid drivers, and inverter applications requiring stable component supply, long-term lifecycle support, and traceable sourcing from original manufacturer stock.

Supply support for KSE5742 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 devices before its acquisition by ON Semiconductor in 2016.

The KSE5742 belongs to Fairchild's high-voltage Darlington transistor family, engineered specifically for ruggedized power switching in inductive load environments including ignition systems, industrial controls, and AC/DC conversion.

FAQ

What is the maximum continuous collector current rating for KSE5742?

The KSE5742 has a DC collector current rating of 8 A at case temperature T_C = 25°C. Derating is required above 25°C per the power derating curve - at T_C = 100°C, maximum I_C drops to approximately 4.5 A. This rating assumes proper heatsinking and ambient airflow per Fairchild's TO-220 thermal guidelines. The KSE5742 must not exceed this limit in sustained operation to avoid junction overheating.

Does KSE5742 include an integrated flyback diode?

The KSE5742 does not contain a separate, isolated flyback diode, but its emitter-base junction exhibits forward conduction (V_F = 2.5 V at I_F = 5 A), which provides inherent clamping functionality during inductive turn-off. This characteristic allows simplified solenoid and relay driver designs without external diodes in many cases. However, designers should verify clamping energy absorption against specific load parameters before omitting discrete protection. The KSE5742's behavior remains consistent with standard Darlington architecture.

What is the safe operating area (SOA) limit for KSE5742 at 10 µs pulse width?

Per Fairchild's Figure 5, the KSE5742's forward-biased SOA at 10 µs pulse width supports up to 250 V collector-emitter voltage and 6 A collector current. This defines the maximum simultaneous voltage/current stress the device can withstand during short-duration switching events. Exceeding this boundary risks second breakdown. The KSE5742's SOA is validated under specified test conditions (V_CC = 250 V, I_C(pk) = 6 A), and must be applied with appropriate safety margins in final designs.

Can KSE5742 replace KSE5741 in an existing design?

Yes, the KSE5742 is a direct upgrade to the KSE5741 with higher voltage ratings: BV_CEO(sus) increases from 350 V to 400 V, and V_CEV from 700 V to 800 V. All other electrical parameters (I_C, P_C, h_FE, V_CE(sat)) remain identical. No layout or drive circuit changes are needed. The KSE5742 maintains full pin compatibility and thermal profile, making it a drop-in solution for enhanced reliability in high-voltage inductive switching applications.

What is the base-emitter saturation voltage range for KSE5742 at full load?

The KSE5742 exhibits V_BE(sat) = 2.5 V at I_C = 4 A / I_B = 0.2 A, and 3.5 V at I_C = 8 A / I_B = 0.4 A. This reflects the dual-transistor Darlington structure's cumulative base-emitter drop. Designers must ensure base drive circuits deliver sufficient voltage headroom - typically ≥5 V - to maintain saturation across temperature and aging. These values are measured per Fairchild's datasheet conditions and apply directly to the KSE5742.