To ensure reliable operation of the VO1400AEFTR solid-state relay (SSR) under worst-case conditions — including maximum specified IFON, high temperature, and long-term degradation — you should calculate the required input current as follows:
Maximum IFON at 25°C:
IFON MAX 25°C = 3.2 mA
Temperature factor (at 85 °C):
IFON MAX 85°C = 3.2 mA x 1.4 = 4.48 mA
Add 20% for aging/degradation:
IFON TOTAL = 4.48 mA x 1.2 = 5.38 mA
Required Current to Turn On the SSR: ≥ 5.4 mA
You should design for a minimum input current of 5.4 mA to guarantee turn-on of the VO1400AEFTR SSR across the entire operating temperature range and over its expected lifetime.
Datasheet: https://www.vishay.com/docs/84724/vo1400aeftr.pdf