Bidirectional TVS for 28 V rails — 1500 W surge capacity
The STMicroelectronics 1.5KE33CA is a bidirectional TRANSIL™ transient voltage suppressor designed to clamp overvoltage events on DC power rails and signal lines. Its 1500 W peak pulse power rating (10/1000 µs waveform) handles industrial surge requirements, while the 28.2 V reverse standoff voltage lets it sit on a 24 V nominal bus without conducting. The 31.4 V minimum breakdown voltage defines the threshold where clamping begins, and the maximum clamping voltage at 169 A peak pulse current is 59 V — the voltage the protected circuitry must survive. A single bidirectional device replaces two unidirectional TVS diodes in antiparallel, saving board space and part count.
Capacitance matters for signal integrity
At 1 MHz the 1.5KE33CA presents 1350 pF of capacitance — typical for a 1500 W bidirectional TVS in this voltage class. On a high-speed data line this capacitance loads the bus and rounds edges; for 24 VDC power inputs, relay coils, or solenoid drives it is transparent. If the protected node carries a communication signal above 100 kHz, check the signal rise time against the RC time constant formed by the source impedance and this capacitance.
Package and mounting — axial DO-201
The DO-201AA (DO-27) axial-lead package is a through-hole form factor suited for point-to-point wiring, terminal blocks, or PCB mounting with 0.9 mm diameter holes. The body is non-hermetic but the axial leads handle high surge currents without trace lift-off — a common choice for bulkhead-mounted transient protection in industrial and telecom equipment.