A typical circuit board system includes an interconnection subsystem and a set of circuit board assemblies. The interconnection subsystem typically includes a card cage, and a backplane mounted to the card cage. Each circuit board assembly installs into a cavity of the card cage and electrically connects to the backplane.
In general, each circuit board assembly includes a circuit board, a row of circuit board connectors disposed along an inner edge of the circuit board and a set of levers disposed along an outer edge of the circuit board. To install a circuit board assembly into the interconnection subsystem, a user (i) orients the levers of the circuit board assembly so that they substantially extend from the outer edge of the circuit board, and (ii) slides the circuit board assembly through an opening of the card cage (inner edge first) so that the row of circuit board connectors along the inner edge of the circuit board moves toward a corresponding row of backplane connectors on the backplane. The circuit board continues to pass through the card cage opening until the levers along the outer edge of the circuit board contact the card cage adjacent the card cage opening. At this point, the levers partially rotate in response to contact with the card cage, and the circuit board connectors of the circuit board align with and partially engage the backplane connectors. The user completes installation of the circuit board assembly by manually continuing to rotate the levers from their partially rotated positions into fully collapsed positions against the outer edge of the circuit board. As the user rotates the levers to their fully collapsed positions, ends of the levers grab the card cage near the card cage opening to leverage the circuit board assembly further toward the backplane thus generating a proper amount of insertion force to push the circuit board connectors into fully mated positions with the backplane connectors. A similar circuit board assembly is disclosed in U.S. Pat. No. 6,185,106, which is entitled “PRINTED CIRCUIT BOARD EXTRACTOR TOOL OPERATED LATCH” and which is assigned to the same Assignee as the present invention, the teachings of which are hereby incorporated by reference in their entirety.
One type of circuit board assembly includes a circuit board having circuitry which is configured to connect with the backplane while the backplane is powered-up or in a “hot” state. That is, a user is capable of installing that circuit board assembly into an empty slot of the card cage while the backplane conveys signals to other circuit board assemblies already installed within the card cage. During installation, when the circuit board connectors make electrical contact with the backplane connectors, the circuitry of the circuit board assembly (i) receives the signals, (ii) performs a power up sequence, and (iii) begins operation.
Such a circuit board assembly is well-suited for fault-tolerant situations in which a redundant but failed circuit board assembly is replaced in a “hot swapping” manner. In such a situation, the user does not power down the entire system. Rather, the user simply removes the failed circuit board assembly and installs a new circuit board assembly while the backplane continues to deliver signals to the remaining installed circuit board assemblies. Accordingly, the system as a whole continues operation in a fault tolerant manner during the replacement process.
One conventional circuit board assembly includes circuitry that requires (i) receipt of only power signals, then (ii) a time delay while the circuitry performs a power-up sequence, and finally (iii) other signals in order to function properly. The circuitry must receive the power and the other signals in this staggered fashion in order to avoid damage and to operate properly. If the circuitry initially receives the power signals and the control signals simultaneously, damage to the circuitry will occur and the damaged circuit board assembly will require replacement.
To avoid damage to such a circuit board assembly, the manufacturer of the circuit board assembly typically warns the user to install the circuit board assembly in a staggered manner when the backplane is in the powered-up “hot” state. To this end, the manufacturer directs the user to (i) partially insert the circuit board assembly into the interconnection subsystem such that longer power supply pins of the connectors connect first, then (ii) wait a short period of time (e.g., at least one or two seconds) so that the circuitry reaches a stable and controlled state, and subsequently (iii) fully insert the circuit board assembly into the interconnection subsystem such that the remaining shorter connector pins of the connectors properly connect. Accordingly, during a “hot swap” installation of the circuit board assembly, the circuitry of the circuit board assembly receives the power signals first, then performs a power-up sequence (e.g., power sequencing operations) without receiving any other signals, and finally receives the other signals in order to properly begin operation.