Many telecom and networking applications require that cards be inserted and extracted from a live backplane without interrupting data or damaging components. To achieve this, interface terminals of the card must be electrically isolated from the bus system during insertion or extraction from the backplane. To facilitate this, Texas Instruments provides bus-interface and logic devices with features such as I(OFF), power-up 3-state (PU3S), and precharge circuits. A combination of these three features, along with the output enable and disable feature, allows the customer to realize a successful live insertion. This application report discusses the concept of PU3S circuitry, its functionality, and the interpretation of data-sheet parameters related to this feature.
For an explanation of I(OFF), precharge circuits, and live insertion, please refer to the TI application report, Logic in Live Insertion Applications With a Focus on GTLP, literature number SCEA026.