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.
For questions regarding this page contact Mircea Bogdan.
bogdan@frodo.uchicago.edu
Revised: May 12, 2005