The 1.5KE100A is a member of the STMicroelectronics 1.5KE Transil™ family, a range of 1500 W (10/1000 µs) avalanche diodes designed to clamp transient overvoltages by conducting heavily once the breakdown voltage is exceeded. The “100” denotes the nominal 100 V breakdown class and the “A” suffix marks it as the unidirectional version, intended for DC and single-polarity rails where the protected line never swings negative.

Under normal operation the device presents only a 1 µA leakage at its 85.5 V stand-off voltage, so it is effectively invisible to the circuit. When a transient drives the line above the 95–105 V breakdown window, the junction avalanches within nanoseconds and diverts the surge current to ground, holding the clamped voltage to a maximum of 137 V at the rated 11 A (10/1000 µs) peak pulse current. For the faster 8/20 µs surge it absorbs up to 56 A while clamping below 178 V.

Because it is supplied in the through-hole DO-201 axial package with a 1 inch lead span, the 1.5KE100A is well suited to board-edge protection on industrial I/O, telecom interfaces and DC power inputs, where its 200 A non-repetitive surge capability and 175 °C junction rating give a generous design margin.

Note: Values are taken from the STMicroelectronics 1.5KE data sheet (Doc ID 2913). Confirm every parameter against the latest data sheet before committing a design.

The 1.5KE100A is supplied in the DO-201 axial-leaded through-hole package. The molded body measures 8.5–9.5 mm in length (dimension A) with a body diameter of Ø4.8–5.3 mm (ØC), and each tinned lead is 25.4 mm long (dimension B) with a diameter of Ø0.96–1.06 mm (ØD). The device weighs about 0.876 g, the epoxy meets UL94 V-0 flammability, and it is offered as a lead-free ECOPACK part.

The dimensioned outline below is the reference for lead forming, hole spacing and clearance when laying out a through-hole footprint or an automated insertion program.

As a two-terminal axial diode the 1.5KE100A has no pin numbers; what matters for correct installation is its polarity. Because the 1.5KE100A is the unidirectional version, the two terminals are not interchangeable:

• Cathode (K) – banded end: The printed band marks the cathode. On a DC line the cathode connects to the positive conductor being protected; the device blocks normal forward current until the line exceeds breakdown.
• Anode (A) – plain end: The unbanded lead is the anode and returns to ground / 0 V, providing the path that diverts the surge current.
• Orientation matters: Reversed, the part conducts as an ordinary forward diode at well under 1 V and offers no clamping, so the banded cathode must always face the protected positive rail.
• Marking: The body is laser-marked “1.5KE100A” per the manufacturer marking table, letting the unidirectional 85.5 V class be identified after assembly.

The closest cross-references come from the same STMicroelectronics 1.5KE Transil™ family. Before substituting, confirm the directionality (A = unidirectional, CA = bidirectional) and the breakdown class, because these determine whether the part suits a DC or a bipolar line and where it begins to clamp.

Selection Comparison

STMicroelectronics (NYSE: STM) is one of the world’s largest semiconductor suppliers, headquartered in Geneva, Switzerland, and one of the original developers of the Transil™ transient-voltage-suppressor line. The 1.5KE series has been a long-running industry-standard 1500 W TVS family, second-sourced widely but defined by the ST data sheet.

STMicroelectronics publishes the governing 1.5KE data sheet (Doc ID 2913) together with the DO-201 mechanical outline used by the 1.5KE100A. That document is the authoritative reference for the breakdown window, clamping behaviour and surge ratings; InFortune Electronics supplies the device and provides sourcing and technical support.