Obsolete — sourcing path and replacement planning
If you are qualifying a replacement, look for a current-production Zener ESD diode in SOD-523 with a 5V reverse standoff and similar clamp voltage. The 80 pF capacitance at 1 MHz is a constraint for high-speed lines — a lower-capacitance alternative (e.g., 0.5 pF to 5 pF) may be needed for USB 2.0 or Gigabit Ethernet ports.
Protection window — 5V rail, 18.6V clamp
The ESD5Z5.0T1 is a unidirectional Zener diode designed to shunt ESD strikes on a 5V or lower signal or power rail. The reverse standoff voltage is 5V max — the diode does not conduct below that. Breakdown starts at 6.2V min, and the clamp voltage peaks at 18.6V at the rated peak pulse current of 9.4A (8/20µs waveform). That clamp ceiling protects downstream ICs rated for 20V absolute max or higher. Peak pulse power is 174W for an 8/20µs surge — enough for IEC 61000-4-2 level 4 (8 kV contact, 15 kV air) on a typical port. The 80 pF capacitance adds about 2 pF of load per inch of trace at 1 MHz; for sub-100 MHz signals the loading is manageable, but for RF or high-speed differential pairs it will degrade eye margin.
Package and inventory — SOD-523 on tape
The ESD5Z5.0T1 is supplied in a SOD-523 surface-mount package, delivered on Tape & Reel. The SOD-523 footprint is 1.6 mm x 0.8 mm — about half the area of an SOD-323. Plan for automated pick-and-place; manual soldering requires a fine-tip iron and magnification. Store the reels in a dry cabinet — the small body wicks moisture quickly, and reflow without bake risks popcorning.