Guidelines for QUIET Electronics Box Module design and P1/P2 pin assignment

May 12, 2005
Mircea Bogdan

Note: This guidelines are preliminary and may change as we advance in the project.  Each change/addition will be logged at the bottom of this page.

1. Chassis

1.1. The QUIET Electronics Box (QEB) is a custom chassis that supports up to 21 modules, placed with a pitch of 0.8".

1.2. QEB is similar in size with a standard 21 slot, VME/VIPA crate. The only difference is the height, which is reduced by 1".

1.2. The entire backplane connector system used is presented here for reference.

2. Backplane

2.1. The Mechanical Drawing of the QUIET Electronics Box Backplane (QEBB)  is actually a customization of a standard 6U VME/VIPA Backplane,  with the height reduced by 1".

3. Modules

3.1. The Mechanical Drawing of the PCBs in the modules is also a customization of a standard 6U Eurocard with the height reduced by 1".

3.2. Each module has two, 160 pin, regular VME, male connectors: P1 and P2 - part # 02 01 160 2101 by Harting. On the PCB footprint of each connector, the pins shall be counted in 5 columns (starting from the edge of the PCB: Z,A,B,C,D) with 32 pins each. (E.g. pin "C8" is the 8th pin from the top, in column C.)

3.3. The modules should  use wedgelock conduction-cooling as in IEEE Std 1101.2-1992. The only difference between this custom design and Std 1101.2, should be the height of the modules (which is reduced by 1"). Conduction-cooling via the module's front panel is not recommended do to the positioning of the chassis mounting flanges close to the backplane.

3.4. All digital inputs to the modules shall be buffered as close to the backplane as possible with stub traces of 1.5" or less. Digital traces shall be designed with Zc = 55 Ohm +/- 10% for single ended and Zd = 110 Ohm +/- 10% for differential (E.g. LVDS).

3.5. For differential lines the backplane pin pair shall be placed on adjacent pins (adjacent columns/same number).

3.6. As much as possible, column "D" should be used for digital ground.

3.7. Unused pins, if any should be chosen in column "B".

3.8. Digital lines should be placed as far as possible from the analog lines.

3.9. If a module provides analog signals, it should also provide the analog grounds, as needed.

3.10. If a module uses galvanic isolated (floating) power lines, the respective "power" and "return" pins should be adjacent.

3.11. The current limit per pin should be 0.7A (the absolute limit is 1.4A).

4. Small Auxiliary Boards & Flex PCBs

4.1. In addition to the above mentioned modules, the QEB supports Small Auxiliary Boards (SABs), one for each backplane connector.  These are ~4" by ~1.5" boards, provided each with a 02 04 160 1101 female Harting connector, that plug in the back and lead  to Flex PCBs and/or wires.

4.2. The trace impedance Zc and Zd for digital traces shall be the same on the SABs and Flex PCBs as described for  the modules in 3.4.