The TPS2342 contains main supply power control, auxiliary supply power control, power FETs for 12-V, -12-V and auxiliary 3.3-V supplies, VIO control, and digital control of slots. Each TPS2342 contains supply control and switching for two slots. The TPS2342 supports both serial and direct communication to the slots. The main power control circuits start with all supplies off and all outputs are held off until all power supplies to the TPS2342 are valid. When power is requested via the serial interface or by direct control, 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 the appropriate gate capacitor. The power control circuits monitor load current and latch off that slot if the load current exceeds a programmed maximum value. Once the 12-V, the 5-V, and the 3.3-V FETs are fully enhanced, the load voltage is monitored. If the load voltage drops out of specification after these FETs are fully enhanced, the slot latches off. The auxiliary power control circuit switches, ramps, and monitors 3.3-V auxiliary power to each slot. The auxiliary control circuit 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 a fault occurs on the board’s auxiliary power. VIO control consists of gate drivers to select between 3.3 V and 1.5 V in response to command over the interface, as well as a regulator for when the 1.5-V supply is greater than 1.575 V and current limiting circuitry to shut down a slot in the event of over current. Each TPS2342 contains power FETs for 12 V, –12 V, and auxiliary 3.3 V 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, LED outputs, and VIO control, and monitors board capability, power fault, and switch input status. The serial interface operates in one of two modes: multi-slot mode and single-slot mode. In multi-slot mode, the data from two or more slots is cascaded on one serial interface. In single-slot mode, each slot has its own independent serial interface. Single-slot mode is preferred when the bandwidth of the bus is so high that the bridge/controller can only manage one slot per bus. The TPS2342 can be configured for a conventional direct mode to access the slot ......