28V reverse standoff — 24V rail clamp threshold
The SMAJ28CE3/TR13 is a bidirectional Zener TVS diode from Microchip Technology, designed to clamp transients on a 28V nominal rail — the reverse standoff voltage of 28V means it will not conduct leakage current below that level, so it sits quietly on a 24V or 28V supply line. That clamping voltage is the ceiling the downstream circuitry must survive.
The -65°C to 150°C junction temperature range covers industrial and military thermal environments without derating the peak pulse power — a common requirement for outdoor telecom or avionics power supplies.