The LTC4242 Hot SwapTM controller allows safe board insertion and removal for two independent slots on a PCI Express backplane. External N-channel transistors control the 12V and 3.3V supplies while integrated switches control the 3.3V auxiliary supplies. Both 12V and 3.3V supplies can be ramped up at an adjustable rate. Dual level circuit breakers and fast active current limiting protect all supplies against overcurrent faults. A supply filter at the VCC pin allows the LTC4242 to endure supply transients. The EN input detects the presence of a card in the PCI Express slot. The FAULT and AUXFAULT outputs alert the system of overcurrent conditions on the main and auxiliary supplies, respectively. PGOOD and AUXPGOOD outputs indicate proper main and auxiliary supply outputs.