What this PhotoMOS relay does on the board
The AQY210EHAX is a normally-open (SPST-NO) solid-state relay from Panasonic's PhotoMOS AQY series, switching AC or DC loads up to 130 mA at 0–350 V.
Load ratings and on-resistance — what they mean for your circuit
Rated for 130 mA continuous load current across the full 0–350 V AC/DC range. The 25 Ohm max on-state resistance (Ron) is the key thermal parameter: at 130 mA, the power dissipation in the output FET is I² × Ron = 0.13² × 25 ≈ 0.42 W. In the 4-SMD package without a heatsink, that keeps the junction rise within the datasheet limit for ambient up to about 85 °C — budget this into your thermal analysis if the relay is packed next to a hot regulator. Because it is a MOSFET-based PhotoMOS, there is no mechanical contact wear or bounce — the switching life is effectively unlimited for signal-level loads. The 350 V blocking voltage covers 240 VAC mains-derived signals with margin, and the AC/DC output type means the same relay works for both polarities without a series diode.
Package and board-fit details
Housed in a 4-SMD package (7.62 mm body width) with gull-wing leads — the 1.27 mm pitch is standard for SOIC-4 footprint layouts. The surface-mount termination and Tape & Reel packaging make it pick-and-place ready for high-volume assembly. No special bake or MSL handling beyond standard JEDEC Level 1 is required for this package type.