LAT Power Supply Peer Review
LAT Power Supply Peer Review
A peer review of the LAT Tower Electronics Module (TEM) power supply design was conducted on September 22, 2003 at SLAC.
The review committee consisted of:
Chairman: Mr. Dick Horn/SLAC
Co-Chairman: Mr. Bernard Graf/GSFC
Members:
-Mr. Jim Trainer)/independent (unable to attend)
-Mr. Fred Huegel/GSFC
-Mr. Arthur Ruitberg /GSFC (unable to attend)
-Mr Steve Battel/independent
Those attending the meeting are listed in Enclosure 1.
A web-site providing the review materials was established prior to the meeting (and is maintained) at:
Overall, the presentation was thorough and well planned. It included all of the electrical, structural, and thermal aspects of the power supply design. During the presentation, there was considerable discussion concerning the LAT and Observatory grounding plans and the related concerns associated with conducted noise. Two action items were assigned.
There were a total of six RFAs submitted (see attached Enclosure 2)
Following the formal presentation, committee members S. Battel and F. Huegel met separately with the design team to review schematics. That session went well, with no significant issues or concerns to report.
With regard to the five questions posed in the charge to the Review Committee, the following summarizes the Committee caucus:
Is the sub-system design maturity, qualification and verification planning at CDR level? Yes.
Has the sub-system identified open design issues and established appropriate resolution plans to ensure closure? In general YES, however there were discussions concerning the use of autotransformers, synchronization signals to each DC/DC converter (not used in current design), and the use of regulators on the Spacecraft for over-voltage protection. In the end, these discussions ended satisfactorily and were not considered open design issues. See attached RFAs.
Is the sub-system near readiness for manufacturing? Yes
Has the sub-system identified open manufacturing issues and established appropriate resolution plans? Yes, however it was noted (see RFA list) the parts stress and derating analysis are not complete and no detailed schedule was presented.
Are there other issues that should be addressed? None that are not captured as an RFA.
We recommend this peer review be accepted as successful.
--Dick Horn, Chair
-- Bernie Graf, Co-Chair
TEM POWER SUPPLY – PEER REVIEW 9/22/03
NameCompanyPhone
B. GrafGSFC301-286-1287
Steve BattelBattel Eng.480-991-9747
Fred HuegelGSFC301-286-2285
Tom VenatorGSFC301-286-3063
Gunther HallerSLAC650-926-4257
Tom LeisgangSLAC/ONE408-245-0726x11
Tony DiVentiGSFC301-286-6507
Dick HornSLAC650-926-8578
Fred Blanchette
Dave Nelson
Lowell Klaisner
REQUEST FOR ACTION (RFA) FORM
GLAST LAT Project
Power Supply Review
Sept 22, 2003
Action Item #
Presentation Section/Subject Area: Worst Case Analysis & Reliability
Specific Request:Complete part stress and derating analysis.
Reason/Comment:
Required per MAR & PAIP.
Submitted by: Actionee:
Tony DiVenti
Organization:
Honeywell/GSFC
Review Co-Chariperson:
REQUEST FOR ACTION (RFA) FORM
GLAST LAT Project
Power Supply Review
Sept 22, 2003
Action Item #
Presentation Section/Subject Area:
Specific Request:Need to get SEU report on Maxim parts out as soon as possible. Issue is not only LET but SET effects since transients can affect the power supply outputs.
Reason/Comment:
Submitted by: Actionee:
Steve Battel GSFC
Organization:
Battel Engineering
Review Co-Chariperson:
REQUEST FOR ACTION (RFA) FORM
GLAST LAT Project
Power Supply Review
Sept 22, 2003
Action Item #
Presentation Section/Subject Area:
Specific Request:Need to get AR-461 filter schematic plus schematic of 28-28 supply on spacecraft. Need to develop model of power and ground distribution to verify filter performance relative to 100 kHz noise. Damping of the entire filter network should also be verified to assure that an interactive among the many identical fitlers cannont occur.
Reason/Comment:
Submitted by: Actionee:
Steven Battel SLAC
Organization:
Battel Engineering
Review Co-Chariperson:
REQUEST FOR ACTION (RFA) FORM
GLAST LAT Project
Power Supply Review
Sept 22, 2003
Action Item #
Presentation Section/Subject Area:
Specific Request:TO-220 Maxim regulators have their mounting tabs connected to ground. This has the potential of creating an undesirable ground path with associated noise problems. The optimum grounding solution for this particular configuration is to connect all elements to chassis and use the structure as the primary ground return (as diagrammed on the conference room whiteboard). It is strongly recommended that this approach be taken to assure proper isntrument performance despite the fact that the approach is slightly unorthodox. As a second issue, it is also suggested that gold foil or indium foil be used to assure reproducible heat sink contact for the regulators. The grease or no intermediate material approaches are strongly recommended against.
Reason/Comment:
Submitted by: Actionee:
Steven Battel SLAC
Organization:
Battel Engineering
Review Co-Chariperson:
REQUEST FOR ACTION (RFA) FORM
GLAST LAT Project
Power Supply Review
Sept 22, 2003
Action Item #
Presentation Section/Subject Area:
Specific Request:Maxim part screening must be carefully done to assure that the testing provides valid verfication reliability. Documented methods by Maxim are for static burn-in only (diffusion based issues) and do not represent the actual operational case planned for GLAST. In that the GLAST application is actually fairly stressful AND uses the part outside of its normal operational range (for the 1.5 volt output case), it is suggested that the screening and qual test be configured to verify the 1.5 volt configuration since it is most stressful. Note that great care must be taken with the layout and instrumentation to assure that the setup does not accidentally result in part damage.
Reason/Comment:
Submitted by: Actionee:
Steven Battel SLAC/Project
Organization:
Battel Engineering
Review Co-Chariperson:
REQUEST FOR ACTION (RFA) FORM
GLAST LAT Project
Power Supply Review
Sept 22, 2003
Action Item #
Presentation Section/Subject Area:
Specific Request:The 28 volt converter planned for use by Spectrum Astro, uses a step-up transformer. A quick calculation indicates that the step-up ratio is probably 1.5 or more. Therefore, a failure where the control loop goes open while the bus is at 33 volts, could have catastrophic consequences to the instrument, such that system level redundancy could be compromised, due to propagation of the failure across interfaces. Therefore, it is strongly recommended that overvoltage protection be implemented to assure protection of the hardware plus protection against failure propagation.
Reason/Comment:
Submitted by: Actionee:
Steven Battel Project
Organization:
Battel Engineering
Review Co-Chariperson: