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Richard Holt – Rutherford Appleton Laboratory ATLAS SCT SP protection options January 2009 Serial Powering - Protection Purpose Protect the stave Assure supply of power to a serial powered chain of modules when one member of the chain fails Control the stave Allow power to arbitrary selection of modules 1 Richard Holt – Rutherford Appleton Laboratory ATLAS SCT SP protection options January 2009 Why add protection? Power failure modes Open circuit module Wire bonding failure Noisy module Without protection, one failed module can adversely affect the operation of all other modules on stave Demonstration staves are very reliable - Protection is not strictly necessary 2 Richard Holt – Rutherford Appleton Laboratory ATLAS SCT SP protection options January 2009 How to add protection? Short out affected module(s) One module out-of-service The switch should respond to module over-voltage and to DCS control 3 -- Switch on -Short out and disable this module Richard Holt – Rutherford Appleton Laboratory ATLAS SCT SP protection options January 2009 Issues to address But… How does the protection do its job? Circuit options default state connections Is automatic protection required? Feedback from hybrid current/voltage How fast must the protection react? Reaction time Is DCS control/reporting required? (yes) Implementation requirements AC coupling Automatic and/or DCS How is the protection controlled? Switching must not affect the rest of the SP chain? Transient effects on problem &/or power-up Bus-cable or hybrid Where should the switch be placed? (hybrid) Numerical failure analysis Quantitative estimate of failure rate? Switch failure modes, fail safe, mass, What extra complexity can we justify? possibility of common mode failure, monitoring Is protection needed for other powering configurations? Note that independent module voltage monitoring may be available through the shunt regulator device if using an “intelligent” component such as SPi, but this may not be possible if there is a an open-circuit module. However, it may be possible to identify a faulty module by switching all modules off, then each one on in turn. 4 Richard Holt – Rutherford Appleton Laboratory ATLAS SCT SP protection options January 2009 Qualitative target specification DCS should be able to switch off (short-out) selected modules Residual voltage (when ‘off’) < 100mV Minimise number of components, area of components and bus-cable lines Position on hybrid is acceptable Over-voltage & over-current automatic protection is desirable Switching a working module on/off must not affect the behaviour of other modules During normal operation (module working) protection draws no power 5 Richard Holt – Rutherford Appleton Laboratory ATLAS SCT SP protection options January 2009 Examples Can we use just one transistor for the task of shorting and SR? OR Less material, but possibility of common mode failure Can we accept the risk of wire-bonds carrying power from bus-cable to hybrid or should protection be placed directly on the bus-cable? OR Easier to implement, but depends on good wire bonding Can SR and protection be included in a single ASIC package? 6 Richard Holt – Rutherford Appleton Laboratory ATLAS SCT SP protection options January 2009 a) Circuit option No active protection This option has been sufficient for demonstration staves. This is a serious option for the ATLAS upgrade. 7 + simple minimum mass, minimum lines engineered redundancy including thick wire bonds & several shunt transistors - Cannot switch modules off Richard Holt – Rutherford Appleton Laboratory ATLAS SCT SP protection options January 2009 b) Circuit option Bonn Each module has a single line to an off-detector controller. This can be used to switch the module off (short it) or to monitor the module voltage. Ref ATLAS Tracker Upgrade Workshop, NIKHEF 3-7 Nov 2008 Powering, Wed 5 Nov 2008, 17:30 Laura Gonella http://indico.cern.ch/conferenceTimeTable.py?confId=32084 OC = Open Circuit (ie switch is “off”, module powered) 8 + simple + control & monitor default state = OC - no fast autoresponse - many bus-cable wires Richard Holt – Rutherford Appleton Laboratory ATLAS SCT SP protection options January 2009 c) Circuit option BNL A common data line fed to a one-wire controller output is latched and used on each module to switch the module off (short it). Ref ATLAS Tracker Upgrade Workshop, NIKHEF 3-7 Nov 2008 Electronics Working Group, Tue 4 Nov 2008, 15:40 David Lynn http://indico.cern.ch/conferenceTimeTable.py?confId=32084 OC = Open Circuit (ie switch is “off”, module powered) 9 + latching control + single DCS wire + fast auto-response default state = OC - no monitor - low residual moduleoff voltage required to hold latch Richard Holt – Rutherford Appleton Laboratory ATLAS SCT SP protection options January 2009 d) Circuit options Villani Similar to the Bonn design, but power is delivered to the onewire controller and latch by the data line. OC = Open Circuit (ie switch is “off”, module powered) 10 + latching control + “single” DCS wire + no trickle power default state = OC - no monitor - no auto-response Richard Holt – Rutherford Appleton Laboratory ATLAS SCT SP protection options January 2009 e) Circuit options Extended As Villani design, but latch may also be set in the safe state using the shunt regulator alarm. Also consider depletion mode FET for fail-safe. SC = Short Circuit (ie switch is “on”, module un-powered) 11 + + + + latching control single DCS wire no trickle power auto-response default = SC - no monitor Richard Holt – Rutherford Appleton Laboratory ATLAS SCT SP protection options January 2009 Comparison Demonstrated Extra area mm2 Extra module mass Extra active module components Extra passive module components Extra bus-cable lines Circuit complexity Minimum (‘off’) voltage Latching Auto over-current protection Auto over-voltage protection Proposal 12 No protection N N N n/a L 0 0 0 0 0 Y Bonn N N N 0 L n 2 1 ? ? ? BNL Y N Y ? M 2 4 3 ? 100 Y Villani N N Y 0 H 2 ? ? ? ? ½ Extended Y Y Y 0 H 2 ? ? ? ? N Richard Holt – Rutherford Appleton Laboratory ATLAS SCT SP protection options January 2009 Summary …circuit options are being implemented and evaluated… 13 Richard Holt – Rutherford Appleton Laboratory ATLAS SCT SP protection options January 2009 End …circuit designs follow… 14 Richard Holt – Rutherford Appleton Laboratory ATLAS SCT SP protection options January 2009 Bonn protection Copied from presentation by Laura Gonella ATLAS Tracker Upgrade Workshop, NIKHEF 3-7 Nov 2008 Powering, Wed 5 Nov 2008, 17:30 http://indico.cern.ch/conferenceTimeTable.py?confId=32084 15 Richard Holt – Rutherford Appleton Laboratory ATLAS SCT SP protection options January 2009 BNL protection IN ZXTDA1M832 PNP-NPN Single Package EDZTE613.6 Module V P 5k SI 1450DH 1k I/O 8 nF Gnd Ds2413 Protection Copied from presentation by David Lynn ATLAS Tracker Upgrade Workshop, NIKHEF 3-7 Nov 2008 Electronics Working Group, Tue 4 Nov 2008 http://indico.cern.ch/conferenceTimeTable.py?confId=32084 16 OUT Richard Holt – Rutherford Appleton Laboratory ATLAS SCT SP protection options January 2009 Villani protection From Giulio Villani, RAL – personal communication 17