PCMCIA power distribution — three-rail switch for card slots
The Texas Instruments TPS2220ADBG4 is a triple-output high-side PCMCIA power switch designed to manage VCC, VPP1, and VPP2 rails in a single card slot. It accepts load voltages of 3.3 V, 5 V, and 12 V, with each output rated for a maximum of 1 A continuous current. The switch integrates fixed current limiting and over-temperature protection to guard against card faults and hot-plug transients.
95 mOhm on-resistance and thermal budget
Typical on-resistance of 95 mOhm sets the conduction loss at 95 mW per amp per output at 25 °C. In a three-output slot drawing 1 A on VCC and 100 mA on each VPP rail, total dissipation sits around 115 mW — well within the SSOP-24 package capability at 85 °C ambient, but the fixed current-limit threshold must be checked against the card inrush profile.
Serial interface and status flag
Control is via a serial interface, which reduces host GPIO count compared to parallel-controlled switches. The status flag output reports over-current or over-temperature faults, allowing the system controller to sequence a card reset or power-down.
The 24-SSOP package (0.209-inch body width, 5.30 mm) requires a standard SSOP-24 land pattern; the 0.65 mm pitch is manageable on two-layer boards with careful fan-out.
Sourcing an obsolete PCMCIA switch
No official successor or second-source alternate is recorded. Confirm the BOM quantity and any date-code requirements before committing.