TPS2340A

SLUS528A – MARCH 2002 – REVISED AUGUST 2002

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APPLICATION INFORMATION

thermal shutdown

Under normal operating conditions, the power dissipation in the TPS2340A is low enough that junction

specifications but remains under the TPS2340A current-limit threshold, power dissipation can be higher. To

prevent any damage from an out-of-specification load or severe rise in ambient temperature, the TPS2340A

contains two independent thermal shutdown circuits, one for each slot’s main supplies.

The highest power dissipation in the TPS2340A is from the 12-V power FET so the TPS2340A temperature

sense elements are integrated closely with these FETs. These sensors indicate when the temperature at these

transistors exceeds approximately 150

°C, either due to average TPS2340A power dissipation, 12-V power FET

power dissipation, or a combination of both.

When excessive junction temperature is detected on one slot, that slot fault latch is set and remains set until

junction temperature drops by approximately 10

°C and the slot is turned off, then on again through the serial

interface. The other slot is not affected by this event. Also, 3.3-Vaux is not affected by thermal events.

digital circuits

The TPS2340A implements two independent slots of hot-plug power management. In addition, the TPS2340A

contains digital circuits to allow communication between these two slots and the system’s hot-plug controller.

Also, the TPS2340A contains inputs for connection to mechanical switches and outputs for driving indicator

LEDs to directly communicate with users and service.

This digital logic implements a serial-to-parallel converter that accepts data from the serial interface and

presents that data to each slot. Data from the serial interface drives the Pwrenx internal main power control

signal. Additional data from the serial interface includes BUSENx and CLKENx outputs to activate bus switches,

RESETx outputs to allow reset to each slot, and ATTLEDx and PWRLEDx outputs to indicate slot status to

users.

The serial-to-parallel converter also accepts data from the slot and sends that data back on the serial interface.

Data to the serial interface includes SWx and BUTTONx switch state, PRSNTnx bits, M66ENx and PCI–XCAPx

bits to indicate board type, and internal fault signals Auxfltx and Faultx.

When the digital circuits are operating in normal mode, the serial interface is enabled and controls the slots. The

TPS2340A also operates in various test modes, allowing board testing and system development.

Each TPS2340A controls two PCI/PCI–X slots. For systems requiring more than two slots, additional

TPS2340A devices can be cascaded without requiring an additional hot-plug controller. To maintain system

reliability and data integrity at full speed, bus length is often limited to six PCI slots. When higher speed PCI–X

protocols are active, bus length may be limited to even fewer active slots. However, the TPS2340A is not limited

in cascade capability or bus length.