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Tracker Power System – Requirements and Studies

Tracker Power System – Requirements and Studies. Katja Klein RWTH Aachen University. CMS Upgrade Workshop May 14th, 2009. https://twiki.cern.ch/twiki/bin/view/CMS/SLHCTrackerPower hn-cms-slhc-tracker-power@cern.ch. Outline. Introduction & requirements Ongoing activities Open questions

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Tracker Power System – Requirements and Studies

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  1. Tracker Power System – Requirements and Studies Katja Klein RWTH Aachen University CMS Upgrade Workshop May 14th, 2009 https://twiki.cern.ch/twiki/bin/view/CMS/SLHCTrackerPower hn-cms-slhc-tracker-power@cern.ch

  2. Outline • Introduction & requirements • Ongoing activities • Open questions • Next steps • Summary & conclusions Tracker Power System

  3. Motivation • Increased granularity & functionality  increase of power consumption • Lower operation voltage  larger currents for same power consumption • Services must be re-used (P ~ I2) • Decrease of material budget highly desirable Novel powering scheme inevitable for the tracker (strips & pixels) Tracker Power System

  4. Powering Schemes Two powering schemes are widely discussed in the SLHC community: Serial Powering and Powering via DC-DC converters Power Task Force recommendation (Jan. 09, chair P. Sharp): “The ‘Task Force’ recommends that the baseline powering system for an upgraded CMS Tracking system should be based on DC-DC conversion, with Serial Powering maintained as a back-up solution. [...] It is important that design decisions taken during this process do not preclude reverting to the back-up solution at a later date.” Converter C converts a “high“ DC input voltage to voltage needed by detector D (V0) • Conversion ratio r = V0 / Vin < 1 • Lower input currents and power losses: Pdrop = RcabI02r2 Tracker Power System

  5. Buck Converters Inductor-based converters provide large currents and are very efficient - the buck converter isoften studied as the simplest inductor-based variant bulky Ferrites saturate for B > ~2T  air-core inductor needed Switching noise radiates noise • Vin 12V • HV-tolerant semi-conductor technology needed •  radiation-hardness Efficiency Material budget Space constraints Schematic scheme of a buck converter (feedback control loop not shown) Tracker Power System

  6. “Charge Pump“ = Switched Capacitors In simple step-down layout: capacitors charged in series and discharged in parallel  Iout = nIin, with n = number of parallel capacitors Capacitors are external  space, mass (but less than coil!) Efficiency No regulation (costs efficiency) Many switches  noise, losses Lowish currents Must be rad.-hard and tolerate Vin Tracker Power System

  7. Strip Power System Requirements • Compatibility with both trigger and tracking layers • A large conversion ratio (depends on tracker power consumption) • Adequate efficiency (depends on r, but roughly > 80%) • Provision of all necessary low voltages: Vana = 1.2V, Vdig ~ 0.9V, Vopto = 2.5V • Provision of ~ 50mA per chip, i.e. ~ 1A per module for outer tracking layers • Provision of up to several Amps for trigger modules (depends on module variant) • Provision of sufficient bias voltage with sufficient granularity • Must not compromise the noise behaviour of the system (depends on FE-PSRR) • Compatibility with existing Low Impedance cables • Low voltage: V < 30V, I < 20A; high voltage: V < 600V, I < 0.5A • Must respect heat tolerance of cable channels • Contribution to material budget as low as possible • Must be small enough to fit (details depend on integration) • Save operation & easy start-up of thousands of modules • Include proper grounding and shielding strategy Note: some of these requirements are in conflict to each other Must find compromise Tracker Power System

  8. Power WG Activities Many useful projects, can only indicate main lines of activity here Tracker Power System

  9. Phase-1: Power to the Pixels • Phase-1 pixel upgrade: 4 barrel layers and 3 end cap disks • FPIX power system layed out for 3 disks, no problem • BPIX: 1612W  2919W (for L = 21034cm-2s-1) cannot be supplied by current power supplies • How to power this BPIX detector? Options being worked out by PSI • Modify & use existing CAEN power supplies (A4603)Status: modified PS in hands, to be tested • Use switched-capacitor DC-DC converters (“charge pump“) • Both for analog & digital power, conversion ratio 1:2 Vana = 1.7V, Vdig = 2.5V  device in HV-tolerant semiconductor process • Only for analog power, conversion ratio 1:2 • Derive Vana from Vdig with 2:3 converter (less cables and connectors);in combination with modified PSs Evaluation of options is ongoing, no conclusion yet Tracker Power System

  10. On-Chip Charge Pump for Pixels Discharging Charging cap- cap+ • Prototype by PSI (`08) • Conversion ratio 1:2 • Iout = 24mA (1 ROC) • 0.25 m IBM CMOS • Ext. capacitors (10-100nF) • Test of noise behaviour with ROC to be done • Future options: version for 1 module (16 ROCs); ratio 2:3 VDD GND Vout del SW2 SW3 SW1 clk GND Output voltage ripple (f=4MHz, C=10nF) 5 mV/div Tracker Power System

  11. Pixel Power Distribution Studies • Fermilab, Iowa, Mississippi • Power distribution studies with pixel ROC (PSI46) • (Commercial) inductor-based converters with various PCB-embedded inductors, switched-capacitor regulators, Serial Powering Interface Chip (developed at Fermilab) • CAPTAN DAQ system with daughter boardsfor DC-DC conversion (ready) & Serial Powering • flexible, powerful DAQ used during integration, can read out 480 ROCs • Measurements have just started Tracker Power System

  12. Development of Converter ASICs • CERN electronics group, F. Faccio et al. • Buck controller ASIC in HV compatible AMIS I3T80 technology (0.35m CMOS) • First prototype “AMIS1“ (summer 2008): working, but large switching losses • Second improved prototype “AMIS2“ submitted, expected back in May 09 • Semiconductor technology is not sufficiently radiation hard • Nevertheless the AMIS2 will be tested within CMS (RWTH Aachen) AMIS2 Vin = 3.3 – 12V Vout = 1.2, 1.8, 2.5, 3.0, 5.0V Iout < 3A fs = 400kHz – 3MHz Tracker Power System

  13. Development of Converter ASICs • Identification of a sufficiently radiation-hard technology is crucial! • New semi-cond. technology: IHP (Frankfurt/Oder) SiGe BiCMOS (SGB25VD) • Irradiation tests of single LDMOS transistors (N and P) X-rays up to 350Mrad TID, protons (24GeV) up to 1016p/cm2 • Sufficienctly rad-hard for r > 20cm • Buck ASIC including all main features submitted by CERN to IHP last week expected back in ~ August • More irradiations planned by CERN electronics group (May/June): • Various generations of IHP LDMOS transistors • AMS 180nm LDMOS transistors • Development of r = ½ charge pumpin 130nm (CERN + external student) • I = 60mA; developed for Atlas, but could also be used in CMS readout chips Tracker Power System

  14. Strip Tracker System Tests • Commercial buck converters used to systematically investigate effects on CMS FE-electronics(Enpirion EN5382D: fs = 4MHz, Vin < 7V) (Aachen) • Aspects studied: ferrite/air-core inductor, solenoid/toroid, Low DropOut reg., shieldingCurrent FE-electronics is sensitive to conductive & radiated converter noise •  Improve PCB layout, develop efficient filtering and low mass shielding (ongoing, report in June meeting) --- No converter --- Toroid converter --- Toroid converter + 30m shield --- Toroid converter + LDO --- T. converter + LDO + 30m shield Tracker Power System

  15. Simulation of Strip Material Budget • Reduction of material is one of the main motivations for novel powering schemes • Simulation of the effect of powering schemes on the MB in CMSSW (Aachen) Total MB of: TEC modules TEC Converters TEC electronics & cables: - 30.0% Original TEC TEC with buck converters r = 1/8 • Many options/layouts have been studied (position, 1-step/2-step, shielding, ...) Typical gain: ~20-30% for electronics/cables, ~5-7% for total MB (Caveat: gain in motherboards is not only due to decreased current) Tracker Power System

  16. Tasks / Open Questions & Next Steps: Pixels • Phase-1 • How to power the pixel barrel detector during phase-1? • Is a switched-capacitor converter needed? • Various options being evaluated (PSI, 2009) •  Charge pump development has started (PSI) • Phase-2 • Are additional buck-like converters on service cylinder needed? • What is their effect on the pixel electronics? •  Investigation of powering schemes on ROC (US, 2009/10) Tracker Power System

  17. Tasks / Open Questions & Next Steps: Strips • Overall system layout must be defined, in particular • conversion ratio (depends on tracker power consumption) • 1-step vs. 2-step scheme (depends e.g. on conversion ratio) • # of converters/module (Vana, Vdig) • integration onto module or motherboards (space, EMI, practicability, etc.) • position of converter (close to module, or higher radii) • bias voltage delivery (problematic, if > 600V are needed) • integration of GBT components (2-3W, some parts need 2.5V) • Specifications for ASIC & PCB, driven by tracker needs • output voltage & current, conversion ratio, switching frequency, tolerable noise level, minimal efficiency, tolerable dimensions etc.  Intense discussion over next couple of months, taking into account the recent layout developments/options  Try to narrow down powering options and develop a consistent scheme until autumn, to streamline powering R&D and guide other WGs Tracker Power System

  18. Tasks / Open Questions & Next Steps: Strips • Interplay with readout ASIC(s)- PS rejection ratio, additional circuitry (regulators, charge pump)? To be understood/decided together w/ FE designers; discussion has started • Cables (not covered) • Power supplies (not covered) • Performance of converter ASIC (efficiency, optimal layout (buck?) etc.) Development of custom buck converter prototypes (CERN, 2009/2010) • Semiconductor technologyIrradiation of transistors from IHP and AMS (CERN, until autumn 2009) • Noise effects on CMS tracker structures System tests with converter prototypes (Aachen, 2009/2010) System tests with SLHC readout chips, hybrids, modules (Aachen, 2010 - ?) • Integration of DC-DC converters into tracker system Developm. & optimization of PCB + inductor (Aachen, CERN, Bristol, 2009/10)Grounding & shielding, system design (> 2010, needs rod prototypes) Tracker Power System

  19. Summary & Conclusions • HV-tolerant rad-hard process identified  important step forward • Development of buck converter ASICs progressing well • Development of switched-capacitor chips started at PSI and CERN • Understanding of noise issues progressing at several institutes • Discussions during next couple of months should lead to a strip powering scheme that obeys all boundary conditions and is technically feasible • Iterate and converge towards Technical Proposals Tracker Power System

  20. Back-up Slides Tracker Power System

  21. R&D Proposals relevant for Power WG 07.01: R&D on Novel Powering Schemes for the SLHC CMS Tracker; by RWTH Aachen (contact person: Lutz Feld), submitted in October 2007; status: approved 07.08: R&D in preparation for an upgrade of CMS for the Super-LHC by UK groups; by University of Bristol, Brunel University, Imperial College London, Rutherford Appleton Laboratory (contact person: Geoff Hall), submitted in October 2007; status: approved 08.02: An R&D project to develop materials, technologies and simulations for silicon sensor modules at intermediate to large radii of a new CMS tracker for SLHC; by University of Hamburg, Karlsruhe University, Louvain, HEPHY Vienna, Vilnius University (contact person: Doris Eckstein), submitted in March 2008; status: approved 08.04: Power Distribution System Studies for the CMS Tracker; by Fermilab, University of Iowa, University of Mississippi (contact person: Simon Kwan), submitted in June 2008; status: approved Tracker Power System

  22. Open Tasks • Cables • Understand consistency of LICs with new powering scheme Looks ok except for bias voltage • Understand how to integrate LICs into new scheme • Cables from PP1 to detector need replacement • Power supplies • Very likely power supplies need to be exchanged • Develop specs, identify and interact with company, test etc. • Need to identify groups willing to take these responsibilities Tracker Power System

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