What this Zener TVS protects and what it doesn't
That standoff is well above a 24V rail — if you landed here searching for 24V protection, this part will not clamp until the line hits nearly 100V, so the downstream circuit would already be damaged. It targets higher-voltage buses: 48V telecom, 72V industrial, or 90V nominal supplies where the transient needs a hard clamp at 178.8V.
Package and temperature — the SQ-MELF and 175°C junction
The SQ-MELF (B case) is a surface-mount package with a cylindrical body that handles high surge currents without cracking the solder joint — common in MIL-spec and high-reliability designs. The junction temperature range spans -55°C to 175°C, so it survives avionics cold-soak and engine-bay heat without derating the 500W pulse at the top end.
Active production — no end-of-life watch needed
Microchip lists the 1N6133US as Active. The base product number is 1N6133, and the US suffix denotes the SQ-MELF package variant.