Part of the Day · SMAJ5.0A — SMA 400W 5V unidirectional TVS diode (marking AE)

Part of the Day · 2026-11-07

An SMA-size 400W TVS diode that clamps transient overvoltages (surges) on 5V power and signal lines. The 5.0 in the part number is the working (stand-off) voltage VR of 5V that may be applied continuously; the breakdown voltage at which it actually starts conducting is 6.40V or more. The body is marked AE.

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 (SMA · top view · approx. 20×)

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

Package SMA · Marking AE

Key specifications

Values are from the Littelfuse datasheet.

Marking and pins

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

Typical uses

• Surge / ESD protection on USB and 5V power inputs
• Protecting 5V logic and communication ports (I/O interfaces)
• Protecting VCC lines in telecom, computer, industrial and consumer equipment (datasheet application example)

Companion & similar parts

• SMAJ5.0CA — Bidirectional type of the same series (marking code WE) — non-polarized with no band, for signal lines that swing + and −
• SMAJ6.0A — VR 6.0V type of the same series (marking code AG) — breakdown 6.67~7.37V, clamping 10.3V
• SMBJ15A — The larger SMB 600W TVS covered earlier in Today's Part — for 15V lines, so not a substitute

A TVS passes almost no current in normal operation, but once the voltage exceeds the breakdown voltage (6.40V~) it conducts and diverts the surge to GND. 5V-class TVS diodes have a relatively large leakage current of up to 800µA, so be sure to check this value in battery-powered devices. During a surge the voltage can rise to as much as 9.2V, so also check that the downstream circuit can withstand it. The top line of the body carries the Littelfuse logo and marking code AE; the bottom line carries the year, month and lot code (YMXXX). Parts with -E at the end of the part number are made outside China (Ex-China).