Part of the Day · SMBJ15A — SMB 600W unidirectional TVS diode

Part of the Day · 2026-10-23

A 600W TVS diode that clamps transient overvoltages (surges) on power and signal lines. The 15 in the part number is not the breakdown voltage but the working voltage (VWM) of 15V.

Actual size

↓ Actual size, left edge aligned to 0 on the ruler

One ruler tick = 1mm. On PC this is actual size on a 24-inch FHD monitor at 100% zoom; on iPhone it adjusts automatically. For other screens, use “Calibrate ruler” below.

Enlarged (SMB · top view · approx. 20×)

Pins The banded end is the cathode — cathode to the line being protected (+), anode to GND

Package SMB

Key specifications

Values are from the Vishay General Semiconductor datasheet.

Marking and pins

Typical uses

• Surge / ESD protection on 12V power inputs
• Absorbing switching surges from inductive loads such as relays and motors
• Protecting sensor and communication signal lines

Companion & similar parts

• SMBJ15CA — Bidirectional type (marking code BM) — non-polarized, for AC and bipolar signal lines
• SMBJ12A — VWM 12V type of the same series — breakdown 13.3~14.7V, clamping 19.9V
• SMBJ18A — VWM 18V type of the same series — breakdown 20.0~22.1V, clamping 29.2V

VWM 15V is the maximum voltage that may be applied continuously; the breakdown voltage at which it actually starts conducting is 16.7V or more. During a surge the voltage can rise to as much as 24.4V, so make sure the downstream circuit can withstand it. Marking code LM follows Vishay (in the same table the bidirectional SMBJ16CA code is also LM, so also check whether the body has a band).