The BTS3405G is a quad low-side MOSFET power switch from Infineon in TSSOP-20, part of the PROFET family (PROtected FET). Each channel contains a vertical N-channel power DMOS transistor with integrated protection and diagnostic features. The input pins (IN1-IN4) are CMOS logic compatible (3.3V/5V) and control the gate of each DMOS switch independently. When IN is HIGH, the DMOS switch turns ON, connecting the load to ground. The typical RDS(on) is 1.0 Ohm per channel at 25C. The BTS3405G provides comprehensive protection: over-temperature shutdown with hysteresis (activates at approximately 170C, recovers at 155C), over-current protection via current limiting (typically 2.5A per channel), short-circuit protection with auto-retry, and load dump protection (up to 40V). The STATUS output pin (not listed in simplified pinout) provides diagnostic feedback when a fault occurs. The ground-referenced load configuration (low-side switch) means the load connects between VBB and OUT, and the switch pulls the load to ground. This is suitable for driving incandescent bulbs, LEDs, relays, and solenoids in automotive and industrial applications. The VBB supply ranges from 5V to 34V (typically 12V automotive battery). The quiescent current is 30uA per channel in the OFF state. The TSSOP-20 package provides adequate thermal dissipation for 1A per channel with a PCB copper pour heatsink.