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Tracker Upgrade Power Working Group Status Report

Detailed report on Tracker Upgrade Power Working Group's activities, challenges, and development of novel powering schemes for SLHC's Tracker Upgrade project.

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Tracker Upgrade Power Working Group Status Report

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  1. Status Report of the Tracker Upgrade Power Working Group Katja Klein 1. Physikalisches Institut B RWTH Aachen University CMS Upgrade Workshop, Fermilab November 20th, 2008

  2. The Tracker Upgrade Power WG Provision of the required power to the front-end electronics has been identified as one of the major challenges for the Tracker Upgrade at SLHC. • A working group has been established in April 2008 • Convenor: K. K. ; second convenor yet to be appointed • Meets roughly every two months • Three meetings so far • https://twiki.cern.ch/twiki/bin/view/CMS/SLHCTrackerPower Task of the WG: Identify and investigate novel powering schemes; identify and develop a solution (solutions) for the tracker subsystems; develop a working system including all relevant components. Status Report of the Tracker Upgrade Power WG

  3. Powering Schemes Parallel powering with DC-DC conversion Serial powering Vdrop = RI0 Pdrop = RI02 Conversion ratio r = Vout / Vin << 1 Pdrop = RI02n2r2 + Classical grounding, readout & communication + Flexible: different voltages can be provided + Several conversion steps can be combined – Radiation-hard, HV and magnetic field tolerant DC-DC converter to be developed – Converter efficiency 70-90% – Converters are switching devices  noise – Inductors must have air-cores  noise + Many modules can easily be chained + No noise problems observed so far – Each module has its own ground potential – All communication must be AC-coupled – Shunt regulator and transistor to take excess current and stabilize voltage Significant local inefficiency – Safety issues Status Report of the Tracker Upgrade Power WG

  4. The Buck Converter (Inductor-Based) The “buck converter“ is the simplest inductor-based step-down converter: Switching frequency fs: fs = 1 / Ts Duty cycle D: D = T1 / Ts Convertion ratio r < 1: r = Vout / Vin = D • Can provide relatively large currents (several Amps) • Technology must work in a 4T magnetic field  since ferrites saturate at lower fields, air-core inductors must be used • Need to find compromise between high efficiency (low fs) and low noise (high fs) • Discrete components (coil, capacitors, ...) need space and contribute to material Status Report of the Tracker Upgrade Power WG

  5. Isolated Converters (Transformer-Based) The “forward converter“ is the most commonly used isolated buck converter: r = n3/n1D D  1 / (1 + n2/n1) • DC isolation between input and output • Multiple outputs with different voltages are possible • Magnetic energy is transfered, not stored → low noise • Air-core transformer needed • More components → more material and higher space demand Status Report of the Tracker Upgrade Power WG

  6. The Charge Pump (Capacitor-Based) Step-down layout: capacitors charged in series & discharged in parallel n = number of parallel capacitors Iout = nIin r = 1 / n • In • → • Inductorless technology • Everything but capacitors is integrated on-chip  low mass, low space • Provides relatively low currents (~ 1A) • Fixed “quantized“ conversion ratio (e.g. r = ½) • Output voltage cannot be controlled by feedback loop • Switching noise Status Report of the Tracker Upgrade Power WG

  7. Relevant R&D Proposals 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 Status Report of the Tracker Upgrade Power WG

  8. Summary of Activities Status Report of the Tracker Upgrade Power WG

  9. DC-DC Converter Development (CERN) • F. Faccio, St. Michelis et al. (not CMS, but CERN electronics group; good relations) • Buck controller chip “SWREG2“ based on Pulse Width Modulation; in HV compatible AMIS I3T80 technology (0.35m CMOS) • PCB designed and manufactured by Aachen • Submission of second prototype chip to AMIS planned for December `08 • Most crucial issue is to identify a radiation-hard HV compatible technology Vin = 3.3 – 20V Vout = 1.5 – 3.0V Iout = 1 – 2A fs = 250kHz – 3MHz A prototype ASIC buck converter for LHC upgrades, St. Michelis et al., TWEPP-08 Status Report of the Tracker Upgrade Power WG

  10. DC-DC Converter Development (CERN) • Many more activities: • Topology optimization, see belowCustom DC-DC converters for distributing power in SLHC trackers, St. Michelis, TWEPP-08 • Noise measurements, e.g. with TOTEM modulesNoise Susceptibility Measurements of Front-End Electronics Systems, G. Blanchot, TWEPP-08 • Converter and inductor simulation Status Report of the Tracker Upgrade Power WG

  11. Novel Powering Schemes (Aachen) • System test measurements with End Cap petal • Commercial buck converters (Enpirion, Micrel) with ferrite and air-core inductors tested • Custom PCB to integrate converter into system Ring 6 modules • E.g. Enpirion EQ5382D: • fs = 4MHz • Vin = 5.5V • Vout = 1.25V / 2.5V 6.4 6.3 6.2 6.1 Motherboard (ICB) Petal Status Report of the Tracker Upgrade Power WG

  12. Novel Powering Schemes (Aachen) No converterToroid Toroid with LDO Toroid, LDO, 30m Al shield No converter2.5V via S type 0.60 MHz 0.75 MHz 1.00 MHz 1.25 MHz CERN buck • Significant increase of raw noise, in particular with air-core inductor • Both conductive and radiative contributions • Toroids create less noise than solenoids • Linear DropOut regulator reduces conductive noise • Shielding helps • Increasing the distance between converter and hybrid helps • Custom converters (CERN buck, LBNL charge pump): ~20% increase due to conductive noise System Tests with DC-DC Converters for the CMS Silicon Strip Tracker at SLHC, K. Klein et al., TWEPP-08 Status Report of the Tracker Upgrade Power WG

  13. Novel Powering Schemes (Aachen) Standardized EMC set-up to measure Differential & Common Mode noisespectra (similar to set-up at CERN) PS Line impedance stabilization network Load Load Spectrum analyzer SpectrumAnalyzer Copper ground plane Current probe Enpirion 2.5V at load Common mode SWREG2 Vout = 2.5V Common Mode Enpirion 2.5V at load Differential Mode SWREG2 Vout = 2.5V Differential Mode Lutz Feld, 7.10.2008 fs • Next steps: optimization of converter integration; noise injection studies Status Report of the Tracker Upgrade Power WG

  14. Air-Core Magnetic Components (Bristol) • Toroidal air-core inductor manifactured into PCB • 35m copper layers, 30 turns • L = (240 ± 20)H (at 100kHz) • RDC = (205 ± 20) m  too high • Next step: develop inductor with lower resistance • To be used in Aachen system test measurements Power Distribution in a CMS Tracker for the SLHC, D. Cussans et al., TWEPP-08 Status Report of the Tracker Upgrade Power WG

  15. Air-Core Magnetic Components (Bristol) • Air-core planar transformer for transformer-based converters • Finite Element Modelling of magnetic field • Primary current 0.25A, without load: 287nT at 10cm • Primary current 0.25A, 1A load current: 12nT at 10cm • 35m copper shield at 200m distance: 60pT at 10cm, resistive loss = 2.8mW • Next step: development of transformer-based converter (15V  1.3V) • Other activities: single module ARC test-stand, EMC test stand Ip = 0.25A Is = 0A 4:1 prototype Ip = 0.25A Is = 1A Status Report of the Tracker Upgrade Power WG

  16. Powering Distribution Studies (US) • Dedicated power board within CAPTAN DAQ system used for power studies • Focus is on pixel subsystem • Test of off-the-shelf DC-DC converters + regulators • Test of serial powering with Serial Powering Interface Chip (SPi) • Reliability study and failure mode analysis, system modelling • No results yet Simon Kwan, 7.10.2008 Status Report of the Tracker Upgrade Power WG

  17. Development of On-Chip Charge Pump (PSI) • For pixel detector • needed for 4th layer • derive Vana from Vdig • Divide-by-2 prototype • Iout = 24mA (1 ROC) • 0.25 m IBM CMOS • External capacitors • First measurements performed: efficiency, voltage ripple • Next step: combine with ROC & measure noise behaviour Charging Discharging cap- cap+ VDD GND Vout del SW2 SW3 SW1 clk GND Beat Meier, 7.10.2008 Output Voltage: low ripple 5 mV/div Status Report of the Tracker Upgrade Power WG

  18. Powering via Cooling Pipes (Karlsruhe) Proposal by Wim de Boer (Karlsruhe): CO2 cooling pipes used as power leads Max. delta V=1,89 mV - I ~50A Jochen Ebert, 7.10.2008 Pipe x-section varies along length of pipe ~1A Max. delta V=43 mV • Measurements with dummy rod and heater foils have started • Many open questions: noise pick-up, safety, ... Status Report of the Tracker Upgrade Power WG

  19. Upgrade Task Force on Powering Systems A task force, chaired by Peter Sharp, has been established by Geoff. It should discuss and compare different schemes (SP vs. DC-DC) and make a recommendation to the working group. Members:Peter Sharp (chair), Fernando Arteche, Guido Dirkes, Federico Faccio, Lutz Feld, Frank Hartmann, Roland Horisberger, Marvin Johnson, Katja Klein, Alessandro Marchioro, Beat Meier, Mark Raymond. Mandate for Tracker Upgrade Task Force on Powering Systems The Task Force will review all the currently proposed solutions for powering an upgraded CMS Tracker and will propose a baseline solution and one back-up solution for powering the upgraded Tracking Systems. The Task Force will involve those currently responsible for the Powering R&D projects, experts on Powering Systems, experts on Power Transmission, Grounding and Shielding and experts on control and safety systems. The Task Force will report in January 2009. The Report will be supported with the documentation provided by the experts to the Review. Status Report of the Tracker Upgrade Power WG

  20. Today‘s Meeting Charge (by Geoff and Daniela): Phase I power issues: How must pixel electrical services change to allow evolution to a fourth layer and increased endcaps? What voltages and currents will be required? Opinions from pixel system regarding possible DC-DC vs serial power. What components must be developed, by when? Status Report of the Tracker Upgrade Power WG

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