The TPS2340A contains main supply power control, auxiliary supply power control, power FETs for 12 V, –12 V and auxiliary 3.3 V supplies, and a serial interface for communications with and control of slots. Each TPS2340A contains supply control and switching for two slots. The main power control circuits start with all supplies off and hold all supplies off until power to the TPS2340A is valid on all positive supplies. When power is requested via the serial interface, the control circuit applies constant current to the gates of the power FETs, allowing each FET to ramp load voltage linearly. Each supply can be programmed for a desired ramp rate by selecting a gate capacitor for the power FET for that supply. The power control circuits also monitor load current and latch off that slot if the load current exceeds a programmed maximum value. In addition, once the 12-V, the 5-V, and the 3.3-V FETs are fully enhanced, the load voltage is monitored. If load voltage drops out of specification after these FETs are fully enhanced, the slot latches off. This provides another level of protection from load fault. The auxiliary power control circuit switches, ramps, and monitors 3.3-V auxiliary power to each slot. The auxiliary control circuit also controls data switches that connect slot interrupts (power management event [PME] outputs) to the main interrupt PME bus after 3.3-V auxiliary supply is connected. PME is disconnected when a board is turned off or faulted. Each TPS2340A contains power FETs for 12 V at 500 mA, –12 V at 100 mA, and auxiliary 3.3 V at 375 mA for each slot. These power FETs are short-circuit protected, slew rate controlled, and over-temperature protected. The serial interface communicates with a slot controller using a synchronous serial protocol. The interface communicates with the slot, status LEDs, and mechanical switches with individual, dedicated lines. The interface operates from 3.3-V power but inputs are 5-V tolerant. Status LED drivers are capable of driving 24-mA LEDs via integrated open-drain MOSFETs. Mechanical switch inputs have internal pull-up and hysteresis buffers. The serial interface controls slot power, bus connection, and LED outputs, and monitors board capability, power fault, and switch input status.