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| − | == MCEv2 5-MDM Instrument Backplane design notes ==
| + | * [[ MCE CARD Serial-Number Lookup ]] |
| − | Here is the schematic posted for review:
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| − | [[http://www.phas.ubc.ca/~mce/projects/spider-spud-bicep2/system/MCEv2_Inst_Backplane/design/elec/C587-201_A_5MDM_IB/C587-201_INST_BP.pdf | IB schematics]] | |
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| − | For the record, here are some of the design decisions, currently not too late to change them:
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| − | * '''implementation of configurable jumpers '''
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| − | In previous backplane designs, jumpers were implemented either as PCB traces or solder jumpers. The former had the problem of not being configurable as we had to cut traces. The latter had the problem that the assembler wouldn't put the solder jumpers on and since they are not on the BOM, it became hard to track whether they were done or not. Therefore, we settled on the following solution for the new design:
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| − | ** Jumpers for signal pairs have reference designators of JPn and JNn (eg. JP1 and JN1 are signal pair jumpers)
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| − | ** These jumpers are called out on the BOM as zero ohm resistors or DNP (do not populate) parts
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| − | ** Zero ohm resistors will not be used for connect ground planes, copper traces will be used
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| − | * ''' MDM routing of low-noise bias lines '''
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| − | How to divide up the Low Noise Bias Signals between the new Bias Cards.
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| − | ** We need to maintain compatibility with existing Bias Cards which should ground these new backplane signal lines.
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| − | ** Maximizing the number of Low Noise Bias Signals we could get 10 on each of BC1-BC3 for a total of 30.
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| − | ** How we route them to the MDM connectors is limited but we have a few options, what seems to be best to me is
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| − | *** P2 gets LN_BIAS_00 to 08
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| − | *** P3 gets LN_BIAS_09 to 15 (P3 also has DET_BIAS_ORG and PXL_HTR)
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| − | *** P4 gets LN_BIAS_16 to 23 with 1 spare signal (pair)
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| − | *** P5 gets LN_BIAS_24 to 29 with 3 spare signal (pair)
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| − | * '''Mechanical and Cosmetic Changes '''
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| − | ** Include provisions for clamping Hirose connectors
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| − | ** Reorder Resistor Reference Designators so they are in order on the PCB
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| − | * '''Design Concerns '''
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| − | ** A considerable number of signal lines now have 0805 zero ohm jumpers which may be difficult to layout in the space available
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