Low Profile Active PCI Switching ASM
Original Publication Date: 2002-May-08
Included in the Prior Art Database: 2003-Jun-21
In today's highly competitive server market, package density is becoming one of the major selling points of a server. Due to this, space above a PCI card is being minimized. However, even with a dense package all of the function must remain in the server. This includes Hot Plugging or Hot Adding PCI cards. With little or no room above the PCI cards, the switching and latching mechanism for Hot Plugging PCI cards has to be extremely space conscious. This invention provides a method of switching the power on or off to a specific switch for a PCI card while also properly retaining the card in the system during the shock and vibration experienced during shipping. Switching the power on or off to the PCI card to an individual card must be automatic while removing a card, and the method for releasing the latching mechanism must be intuitive and capable of being actuated with a single hand. This invention fully solves all of these problems at lower price than the current method. This invention consists of a horizontally mounted switch card (Figure 1), a modular base design, latch, actuator, pivot pin, and spring, see Figure 2. All of these items must be incorporated into a design that is reusable across multiple platforms, modular in design, intuitive, and extremely space conscious. Current systems have a Hot Plug mechanism cross section that is 28 mm high by 31mm deep. This low profile switching mechanism reduced the height of the mechanism to 5.5 mm while only increasing the depth to 35 mm. Since the 5.5 mm height is fully contained below the top edge of the PCI card, this mechanism is not dependant on the space above a card and therefore it does not waste any vertical space. This is a requirement for 3U systems, because there is minimal clearance between the top cover and the top of the PCI cards. Figure 1 shows the circuit board design. This is a horizontally mounted board in order to save space. The board has one optical switch for each Hot Plug slot mounted to it. These optical switches are normally open which tells the system to provide power to that particular slot. When the switch is broken the system must shut down the power to the slot. If the user does not shut down power to the slot, and then tries to Hot Plug a system, the system could crash. To prevent this, the switching of the slot must be automatic when removing a card. The method for solving this problem can be seen in Figure 4. First, a description of how the mechanism works. Figure 2 identifies all of the parts to the mechanism, and Figure 3 shows the method for removing a card. In Figure 3 , the slot indicated by a one shows a latch in its fully closed state with a card installed. Slot two shows the spring loaded actuator slid back toward the rear of the box. When this is done, the switch is broken, and the power is turned off to the slot. Slot three then shows the latch rotated 105 degrees so that the user has access to the PCI card. When this latch is rotated, a tab on the latch blocks the actuator from being sprung forward and thereby prevents the power from being turned back on to the slot until the latch is in its fully closed position. Finally, slot four shows a partially removed card. In Figure 4 , one can see that the optical switch is not blocked by the actuator when it is in the locked or forward position. Then in the second view, the actuator in the unlocked or rear position fully blocks the optical switch. As mentioned earlier, the actuator is spring loaded forward. This is done with an integrated leaf spring in the EMC shield. The spring can be seen in both Figures 2 and 5 . The EMC shield is obviously required for EMC purposes and therefore is included in every box. So by integrating the spring into the EMC shield allowed for an essentially free spring.