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Requirements for an Outer Tracker Power System and First Conclusions

Requirements for an Outer Tracker Power System and First Conclusions. Katja Klein 1. Physikalisches Institut B RWTH Aachen University. Tracker Upgrade Power WG Meeting June 4 th , 2009. Preface. This is not a proposal for a power system

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Requirements for an Outer Tracker Power System and First Conclusions

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  1. Requirements for an Outer Tracker Power System and First Conclusions Katja Klein 1. Physikalisches Institut B RWTH Aachen University Tracker Upgrade Power WG Meeting June 4th, 2009

  2. Preface • This is not a proposal for a power system • Objective is to summarize available relevant informationand start to understand consequences • This talk is meant to trigger a discussion (today and duringnext couple of months) Outer Tracker Power System Requirements

  3. Outline • Short introduction of three main strawman layouts • Total power consumption and conversion ratio • Cable specifications and conversion ratio • GBT • Bias current and voltage • CMS Binary Chip • Implementation of a DC-DC buck converter • Discussion of options for DC-DC conversion • Conclusions Outer Tracker Power System Requirements

  4. Track Trigger • We think we need to provide information from the tracker to the L1 trigger • This leads to a very different tracker • Large power consumption (see later) • Two methods; both discriminate between low and high transverse momentum tracks J. Jones (~2005) CMS Tracker SLHC Upgrade Workshops Cluster width G. Parrini, F. Palla (TWEPP2007) Stacked modules α Outer Tracker Power System Requirements

  5. “Hybrid Strawman“ • Two trigger layers with stacked modules at 25cm and 35cmPixel size 100m x 2.37mm; dstack = 2mm • Outer tracker similar to today, but shorter strips (4.5cm) • 11 million strips, 300 million pixels (in the simulation) • Outer tracker FE-power ~ 24kW (reminder: strip tracker today needs 33kW for FE + links) Outer Tracker Power System Requirements

  6. “Long Barrel Double Stack Strawman“ • Whole tracker built of pixel modules with trigger capability • 3 full + 2 short superlayers of double stack modules • Pixel size 100m x 1mm • No end caps • FE-power ~ 100kW Outer Tracker Power System Requirements

  7. [Cluster Width Approach] • 4 barrel layers, starting at 45cm radius (+ end caps) • Short strips (2.5cm, 4.5cm) • Must be combined with yet to be defined inner layers • FE-power ~ 21kW four 4 barrel layers only Outer Tracker Power System Requirements

  8. Comparison of Layouts Goal is to understand consequences for a power system, not to judge about the proposals! All power numbers include a DC-DC efficiency of 80% § Variant with 2 long barrel pT layers and tracking-only endcaps ° Only four barrel layers, inner layer starting at 45cm $ assuming 10Gb/s GBT-like link, 2W per link & with 2W/GBT % depends on optical module (GBT vs. MZM), larger number for GBT (3W per GBT) * for A = 85cm2 # depends strongly on module proposal Outer Tracker Power System Requirements

  9. Total Power Consumption • Total power consumption limited by heating up of water-cooled cable channels • Today the total current in cable channels is 15kA • Upper limit would have to be determined by measurements on mock-ups of hot spots in cable channel (Hans Postema) • 10-20% more might be possible, but probably not more? (Hans Postema) • Can calculate maximum power consumption for certain convertion ratio r = Iin / Iout: E.g. for r = 1/10 and 80% efficiency: Pmax = 150kA x 1.2V x 0.8 = 144kW • Can estimate the necessary conversion ratio for a given power consumption: r = 15kA / Iout P = Uout x Iout (includes already converter efficiency of 80%) r = 15kA x Uout /P Outer Tracker Power System Requirements

  10. Specs of Low Impedance Cables • The 1944 Low Impedance Cables (LICs) must be re-used • Low voltage conductor: 50 enamelled wires of 0.6mm2 in 2 concentric layers • 10 twisted pairs (AWG26) at the centre: 5 x HV, 2 x sense, 3 x (T,H) • 13nH/m, 7nF/m, Z0 = 1.4 • Specification of LV conductor: Umax = 30V, Imax = 20A (return) • Specification of twisted pairs: Umax = 600V, Imax at least 0.5A (Simone Paoletti) Outer Tracker Power System Requirements

  11. Specs of PLCCs • 356 standard multiwire cables, now used for control power • Slightly different design for TIB/TID (# = 120), TOB (# = 92), TEC (# = 144) • E.g. TEC: 2 twisted pairs (AWG28), LV: 2 x AWG14 (43x0.25mm) = 2 x 2.11mm2 • Specs for LV: Umax = 30V, Imax = 15A for TEC and 20A for TOB/TIB (S. Paoletti) • We can probably not afford not to use these cables TIB/TID TOB TEC Outer Tracker Power System Requirements

  12. Conversion Ratio from Cable Specs • Assume only 1 000 LICs can be used to power the modules (reason: next slide) • Umax = 30V, Imax = 20A (return) • Calculate mean number of modules per LIC • Calculate mean current per LIC • Estimate necessary conversion ratio • In reality, could try to level out (but then granularity becomes an issue) Outer Tracker Power System Requirements

  13. GBT Transceiver: clock generator, de/serializer, de/encoder, error correction... Photodiode P. Moreia (ACES, Back-up slides, preliminary) Laser • Power per GBT = 2 – 3 W • GBLD (450mW) & GBTIA (115mW) need 2.5V • Other circuitry (~ 2.5W) needs 1.2V • Two converters needed per GBT? Transimp. amp. Laserdriver Slow control ASIC Outer Tracker Power System Requirements

  14. Powering the GBT • In many proposals, GBT components are placed outside of sensitive volume mass/space less of an issue • Number of GBT links needed depends on proposal Example hybrid layout: ~ 7 500 GBT links (Duccio): • 1 GBT per module for trigger  6 272 GBT links • 1 GBT per rod for readout of outer barrel layers • 36 GBTs per disk for readout of endcaps • 2 GBTs per rod for readout of trigger layers • How many GBT links per power cable? Granularity/safety issue! • Recall: we have ~ 2300 (LIC + PLCC) cables for GBT + module power • Assume per power cable: 10 GBTs (modules) for trigger, 2 GBTs (rods) for readout of outer tracker, 4 GBTs (2 rods) for readout of trigger layers: 1 127 GBT power lines • This leaves us with ~ 1 000 power cables for the modules • Do we really want to put 7 500 (x2?) DC-DC converters on the bulkhead or PP1? Outer Tracker Power System Requirements

  15. Bias Current & Voltage • Assume again 1 000 LICs, each with 8 HV groups = 8 000 HV groups • Today 4 HV lines share the return line • Granularity similar to today, up to 10 modules per return line • Current spec (0.5A) should be ok (next slide) Outer Tracker Power System Requirements

  16. Bias Current Alberto Massineo Example: A = 10cm x 10cm = 100cm2 100mA 10mA 1mA  For R > 18cm current is < 10mA per 100cm2 sensor Outer Tracker Power System Requirements

  17. Bias Voltage PET von Y. Unno (KEK) n-in-p Flowzone irradiation G. Casse, A. Affolder • Charge collection increases with bias voltage  do we need bias voltages > 600V? • Not excluded, but would require careful tests & re-qualification of cables • Atlas: have 2000 TRT cables which can stand 1kV; are considering piezo-electric step-up converters and installation of additional HV-cables Outer Tracker Power System Requirements

  18. CMS Binary Chip • Vana = 1.2V • Probably Vdig < Vana (~ 0.9V) • P = 64mW per Chip (26mW analog power, digital power ~ halved with 0.9V) • Both analog and digital currents ~ 21mA per chip • Shaping time 20ns  highest noise sensitivity around 8MHz low DC-DC switching frequency preferred • Input voltage required to be  5% of nominal • How to provide the two voltages? To be better understood. • Use the two LV conductors in LICs and two separate buck converters • Provide one input voltage, use two separate buck converters • Derive Vdig from Vana with linear regulator (efficiency?) • Derive Vdig from Vana with charge pump (ratio 4:3) Outer Tracker Power System Requirements

  19. CMS Binary Chip Spice simulation (Mark); large pulse = 4fC (25 000e) small “pulses“ due to converter ripple; no external filtering  1000e 10mV Output ripple on 2.5V; measured in Aachen • Ripple of Aachen PCB with Enpirion chip measured with active differential probe • Introduced noise of ~ 1000e is of same order as FE-noise  not acceptable? Outer Tracker Power System Requirements

  20. Integration of Buck Converters Aachen PCB: INDUCTOR ~ 1cm CERN PCB (proposal): ~ 3cm SMD SMD SMD ASIC SMD 1.5-2 cm 1.5-2 cm  Space (currently) needed per buck converter: 2-4cm2 Outer Tracker Power System Requirements

  21. Outer Tracker Module Proposal • Duccio Abbaneo, Frank Hartmann, Karl Gill 2 x 4-MUX + LCDS driver each output 160Mbit/s TCS I/O PLL DC-DC shielded micro-twisted pairs I/O DC-DC out 2.5V Sensor HV • 2 x 5cm or 4 x 2.5cm strips • Integrated pitch adapter • 6 or 12 CBCs • Per CBC: 2 x 128 channels • CBC-power ~ 0.75W per hybrid; i.e. 0.75W or 1.5W per module • Plus DCU, PLL, DC-DC inefficiency, GBT-port, MUX, LCDS-driver • No motherboards • Upper part of hybrid ~ 2.5cm x 1cm, no space for buck converter available 8x CBC 2x 128ch wire bonded 40Mbit/s out each Sensor with 4x2.5cm strips 2x 1024 @95um pitch integrated pitch adaptor 2.5cm DCU Outer Tracker Power System Requirements

  22. Vertically Integrated Hybrid Module Proposal by M. Mannelli et al. • Module for double stack proposal • Modules integrated onto “beams“ • Sensor area = 85cm2 • 90nm • Communication through vias in ROC and interposer (3D-integration) • No motherboards • FE-power 4-9W per stacked module • Up to 10A per stacked module • Charge pumps no option • Two buck converters per stack • No space on module; no hybrid • Integrate buck converters into beam structure Outer Tracker Power System Requirements

  23. Trigger Module • For pT-layers in hybrid layout • 90nm • Sensor size = 4.8cm x 4.8cm • Hybrid ~ 1cm x 4.8cm • No space for buck converter • Power per pT-module = 2.6W • I per modul ~ 3A • Single charge pump no option • 170mA per chip but 90nm, no space for capacitors etc. Proposal by S. Marchioro 1 Modul: 1 Chip: Outer Tracker Power System Requirements

  24. Trigger Module Proposal by G. Hall data out control in 26mm 80mm • For pT-layers in hybrid layout • Sensor size ~ 2.6cm x 8.0cm • Hybrid ~ 1cm x 4cm • Again no space for buck converters • Power per pT-module ~ 1.3W • Current per single module ~ 600mA • Could imagine here one charge pump per module with r = ½ Outer Tracker Power System Requirements

  25. Integration of Buck Converter • There is a tendency to avoid motherboards at all • Outer tracker module, vertically integrated double-stack proposal, others? • This goes hand in hand with rather minimalistic hybrids of a few cm2 • All existing or planned buck converter PCBs need an area of 2 - 4cm2 • Suggestion:a separate buck converter PCB close to the module, e.g. inside the beam (for double-stack approach) or on the rod/stave • converter needs cooling contact – probably not too dificult then • need short power cable between converter PCB and module • Could/should be designed such that it fits with all proposals/applications: • Version with 1.2V and 0.9V for CBC • Version with two buck converters for high-power trigger modules • Version with 1.2V and 2.5V for GBT, for PP1 or bulkhead Outer Tracker Power System Requirements

  26. Integration of Buck Converter • Arguments for buck converter on separate PCB, close to module: • Very limited space on most proposed hybrids  size less critical • Larger distance preferred for EMI anyway (also damping of ripple?) • Converter development completely decoupled from hybrid and module development • No common deadlines, can optimize converter design as needed (even late) • Different hybrids for different module proposals  many groups involved • PCB could be developed, manifactured and tested standalone • Easier for cooling? (module cooling is difficult enough without converters) • Arguments for buck converter on the module/hybrid: • Less mass (avoid connectors & connection between converter and module) • Power regulation closer to FE-ASICs (only relevant if no LDO) • Could have pluggable PCB on hybrid, but then connectors are needed (mass) • Noise effects can be tested more easily (don‘t need additional PCB) Outer Tracker Power System Requirements

  27. Discussion • Discuss in the following three scenarios • Only charge pumps • Only buck converter • Two step scheme with both buck converter and charge pump • Then some comments on charge pumps and LDO regulators Outer Tracker Power System Requirements

  28. Scenario A: Only Charge Pumps • Avoid buck converters or place them further outside (TEC Bulkhead, PP1 ...) • Use only charge pump, assume r = ½ or ¼ • Charge pump either per module or per chip (do not distinguish here) • Pros: • Only one technology to deal with • Do not need to find space for buck converter • No radiated noise from air-core inductor • Cons: • Some proposals need r ~ 1/10 • Some proposals need too large currents (must be <1A per charge pump) • For r = ¼, special HV-tolerant semiconductor process needed (as for buck) • Additional chip(s) plus capacitors on the FE-hybrid • Regulation only on cost of efficiency; a LDO regulator is needed in addition • Studies show that buck converter (r = 1/8) close to module saves material  Scenario with charge pumps only no reasonable option Outer Tracker Power System Requirements

  29. Scenario B: Only Buck Converters • Avoid the use of any charge pumps • Assume buck converter close to the modules with r = 1/6 or smaller (as needed) • Pros: • Only one technology to deal with • No additional chips on the FE-hybrid • No influence on FE-chip design/layout • No need for additional regulation • No switching device very close to or inside the FE-chips • Cons: • Must provide relatively high conversion ratio in one step (efficiency, noise?) • Need to find space for buck converter(s) on or close to the module  Considerable lower complexity, few disadvantages Outer Tracker Power System Requirements

  30. Scenario C: Both Buck + Charge Pump • Buck converter with r  ¼ close to module • Charge pump with r = ½, either per module or per chip • Pros: • Can switch off single chips • Easy start-up, can power only the “controls“ • Cons: • Two technologies to deal with • Has basically all disadvantages of both previous options  Complex system; arguments should be compelling Outer Tracker Power System Requirements

  31. Integration of Charge Pump • Pro for separate charge pump chips (per module or per readout ASIC): • No constrains of layout of readout ASICs • No risk of substrate noise • Same chip could be used with different FE-ASICs • On-chip no option for highly integrated approaches (needs external components) • More flexible: can be used with some proposals, omitted in others • Could power also auxiliary FE-ASICs (PLL, DCU, ...) • If one charge pump per readout ASIC: • more capacitors • possibility to switch off single readout chips • Pro for charge pump as part of readout ASICs: • More integrated approach, no separate chips to be produced, tested, integrated onto hybrid Outer Tracker Power System Requirements

  32. Integration of LDO • A LowDropout Regulator (LDO) could be needed to • filter ripple on the power line (but new Aachen measurements show that filter can be just as good) • regulate the output voltage of the charge pump, which has no own regulation; neccessity depends on the requirements of FE-ASICs on the PS • regulation needed only for analog part • Efficiency loss of a few per cent • Additional part in FE-ASIC (currently not foreseen) • Needs to be radiation hard Outer Tracker Power System Requirements

  33. Conclusions • Conversion ratio depends on proposal, between 1/2 und 1/10 • Buck converters cannot be avoided (but charge pumps can) • No motherboards and no or very small hybrids integrate buck converter onto separate small PCB • Must understand better if charge pumps are needed and gain experience • Only experience: Aachen tests with LBNL charge pump: excessive noise • Must understand better if an LDO is needed • Many cables will be needed to power GBT • Need input from sensor WG on bias voltage Outer Tracker Power System Requirements

  34. Next Steps • Follow-up meeting with Federico (tomorrow) • Power session in Tracker Upgrade Project Office (June 10th) • Understand better the possible options: talk by Federico on maximum conversion ratio, currents, efficiency etc. in next power WG meeting • In the meantime: watch progress on proposals & start discussion • Write up buck converter specifications Outer Tracker Power System Requirements

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