PCMCIA power switch array — four sockets, one controller
The Texas Instruments TPS2224ADBG4 is a PCMCIA power switch array integrating four high-side outputs with a serial interface for slot control. It handles the 3.3 V, 5 V, and 12 V rails typical of PCMCIA card slots, switching up to 1 A per output through a 95 mOhm typical Rds(on) pass element.
At 1 A per output, the 95 mOhm typical on-resistance drops about 95 mV and dissipates 95 mW per channel.
Protection set — fixed current limit and thermal shutdown
The TPS2224ADBG4 includes fixed current limiting and over-temperature protection on each output. The current limit is a fixed threshold — no external resistor sets it — so the 1 A continuous rating is the design ceiling. If a card draws past the limit or the die hits the thermal trip, the output latches off and the status flag asserts through the serial interface.
3:4 input-to-output ratio — supply mapping matters
The 3:4 input-to-output ratio means three supply inputs (3.3 V, 5 V, 12 V) are distributed across four outputs. Not every output can independently select a rail — the mapping is fixed per the PCMCIA standard. Verify the slot power sequencing requirements against the TPS2224's internal mux before committing the BOM.