| 摘要 |
A self-shutdown system for a circuit card when removed from the connector of a primary system, where the circuit card includes a local power source for providing power when primary power is not available. A dedicated sense pin on the connector of the card is grounded to the remaining ground pins when the card is plugged in but floats or is otherwise disconnected when the card is unplugged from the primary system. A ground switch circuit connected to the sense pin and the remaining ground pins asserts a shutdown signal for disabling the circuitry on the card when the ground sense pin is floating or deasserts the shutdown signal when the ground sense pin is grounded. In one embodiment, the disable mechanism is a switch circuit for disconnecting the main circuitry of the card from the local power source. In the preferred embodiment, however, a DC/DC converter receives the shutdown signal and disables the remaining circuitry when the shutdown signal is asserted. In this manner, the main circuitry of the card is disabled and thereby protected in the event the unplugged card comes in contact with conductive surfaces which might otherwise damage the enabled card. A manual override switch or jumper can be used to disable the automatic shutdown system.
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