DSB Design Review

1
DSB Design Review

• May 5, 2004
• Gerald Przybylski
• Lawrence Berkeley National Laboratory

2
Deficiencies of Rev 0

• Loading irregularities/Fab deficiencies
• Footprint irregularities
• Short across manual reset switch
• 1Hz, 50 duty cycle limitation on 1pps input
• On-board 3.3V regulator undersized
• Mode switching threshold marginality
• Reset pulse switch accessibility

3
Mitigations

• Fab issues- Require Class II fabrication in
  purchase order
• Change layout for selected, incorrectly sized
  footprints - R66 R68 pads to 1210 size-
  Change Y1 footprint. Three of 5 pads out of
  position- Suggest change 1uF Capacitors, C18,
  C23, C24, C27, C36, C38, C44, C45, C50, C58, C61,
  C63, C65, C67, C68, C72 and C74, to X7R Ceramic
  (DC020703FIF) 0805 size- Shorten board by 1/16"
  (?)

4
Mitigations (continued)

• Change regulator U2- Mpack part (digi-key
  LP3964EMP-3.3CT-ND by National Semiconductor)
• S1 Use only pin 1, pin 2, the switch contacts.-
  Correlate with footprint
• Modify 1pps input from GPS- R63 becomes open
  circuit,- C40 (from JP3 to U13-2) becomes R119
  4.7K
• Change LEDs and switch to improve accessChange
  DS1, DS2, DS3 to a three-in-one verticle LED unit
  DS1a,b,c, - (suggest digi-key 350-1274-ND)-
  Correlate with End-panel layout change
• Shorten board by 1/16"

5
Enhancements

• Add fuses F1, F2, F3
• Add four protective diodes, D9, D10, D11 and D12.
• Add ground pins on JP2A and JP2B
• Add ground pins on JP3 (RJ45 input connector)
• Add provisional loading instructions to build
  instructions to loading house
• 0 to 1 transition on a modem control line causes
  pulse from 1pps fan-out

6
Status

• Schematics revised
• New BOM
• New Netlist for PADS
• Unresolved PADS version compatibility

7
Wish List,if there ever is a V2.x

• Add PCI interface- CPLD or FPGA- Driver
  needed- Config memory
• Add Power and Fan monitoring capability- 48V
  monitoring not provided by off-the-shelf monitors
• Add remote power on/off functionality- requires
  remote power (CANbus or POE)
• Add remote CPU Reboot functionality