55 mOhm high-side switch with auto-restart and fault protection
The Infineon IPS521STRL is a single-channel high-side N-channel power switch in a D2Pak (5-Lead) surface-mount package. It switches a load supply from 5.5 V to 35 V and delivers up to 1.9 A continuous output current, with a typical on-resistance of 55 mOhm. The switch is self-contained — it requires no external Vcc supply to operate (the gate drive is bootstrapped from the load voltage). Built-in fault protection includes current limiting (fixed threshold), open-load detection, and over-temperature shutdown. The auto-restart feature means the switch re-tries after a fault clears, which is useful for driving lamps or motors that present a momentary short at turn-on.
Load budget and thermal reality
The 55 mOhm Rds(on) at 25°C junction sets the conduction loss floor: at 1.9 A the dissipation is about 200 mW. That figure doubles at 150°C junction because silicon Rds(on) roughly doubles with temperature. The D2Pak's exposed tab soldered to a large copper plane on the PCB is the primary heat path — without adequate copper area the junction temperature climbs above the 150°C absolute maximum and the over-temperature protection cycles the output. The 35 V maximum covers 24 V industrial rails and 12 V automotive systems with headroom for load-dump transients.
Package and footprint notes for the D2Pak
The D2Pak (5-Lead) is a surface-mount power package with an exposed metal tab on the bottom. The 5-lead variant has four signal pins plus the tab; the fifth pin is the sense/status output. The package footprint is compatible with standard TO-263-5 land patterns.