Tracker Power System – Requirements and Studies

CMS Upgrade Workshop May 14th, 2009

Katja KleinRWTH Aachen University

https://twiki.cern.ch/twiki/bin/view/CMS/SLHCTrackerPowerhn-cms-slhc-tracker-power@cern.ch

Outline

Katja Klein 2Tracker Power System

• Introduction & requirements

• Ongoing activities

• Open questions

• Next steps

• Summary & conclusions

Motivation

Katja Klein 3Tracker Power System

• 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)

Powering Schemes

Katja Klein 4Tracker Power System

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.”

Two powering schemes are widely discussed in the SLHC community: Serial Powering and Powering via DC-DC converters

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 = RcabI0

2r2

Switching noise

Buck Converters

Katja Klein 5Tracker Power System

Inductor-based converters provide large currents and are very efficient - the buck converter is often studied as the simplest inductor-based variant

Ferrites saturate for B > ~2T air-core inductor needed

Efficiency

Vin 12VHV-tolerant semi-conductor technology needed radiation-hardness Material budget

Space constraints

radiates noise

bulky

Schematic scheme of a buck converter(feedback control loop not shown)

“Charge Pump“ = Switched Capacitors

Katja Klein 6Tracker Power System

In simple step-down layout: capacitors charged in series and discharged in parallel

Iout = nIin, with n = number of parallel capacitors

Capacitors are external space, mass (but less than coil!)

Many switches noise, losses

Must be rad.-hard and tolerate Vin

Efficiency

No regulation (costs efficiency)

Lowish currents

Strip Power System Requirements

Katja Klein 7Tracker Power System

• 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

Power WG Activities

Katja Klein 8Tracker Power System

Topic / Scheme Electronics development System tests Material budget

DC-DC conversion(baseline solution)

Non-isolated inductor-based:CERN (technology, ASIC development, simulation);Aachen (PCB);Bristol (air-core coil)

Aachen (strips) Aachen

Transformer-based:Bristol

Fermilab, Iowa, Mississippi (pixels)

Charge pump:PSI (pixels); CERN (strips)

Piezo-electric transformer: -

Serial powering(back-up solution)

(Fermilab) Fermilab, Iowa, Mississippi (pixels);Rochester? (strips)

Aachen

Implementation Karlsruhe (Powering via cooling pipes): on hold

Power supplies, cables: not covered

Many useful projects, can only indicate main lines of activity here

Phase-1: Power to the Pixels

Katja Klein 9Tracker Power System

• 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 = 21034cm-2s-1) cannot be supplied by current power supplies

• How to power this BPIX detector? Options being worked out by PSI

1.Modify & use existing CAEN power supplies (A4603)Status: modified PS in hands, to be tested

2.Use switched-capacitor DC-DC converters (“charge pump“)

a. Both for analog & digital power, conversion ratio 1:2 Vana = 1.7V, Vdig = 2.5V device in HV-tolerant semiconductor process

b. Only for analog power, conversion ratio 1:2

c. 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

On-Chip Charge Pump for Pixels

Katja Klein 10Tracker Power System

VIN

VOUT

C1

C2

VIN

VOUT

phi 2C1

C2

phi 1

phi 1

phi 2

phi 2

phi 1

phi 1

phi 2

cap+cap-

VDD

Voutdel

clk

SW1

GND

GND

SW2SW3

f [MHz]

P_SC P_Ri Pout

10 2 % 14 % 84 %

20 4 % 15 % 81 %

40 8 % 18 % 74 %

• 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

5 mV/div

Output voltage ripple (f=4MHz, C=10nF)

Charging Discharging

Pixel Power Distribution Studies

Katja Klein 11Tracker Power System

• 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 boards for DC-DC conversion (ready) & Serial Powering

flexible, powerful DAQ used during integration, can read out 480 ROCs

• Measurements have just started

Development of Converter ASICs

Katja Klein 12Tracker Power System

• CERN electronics group, F. Faccio et al.

• Buck controller ASIC in HV compatible AMIS I3T80 technology (0.35m 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 – 12VVout = 1.2, 1.8, 2.5, 3.0, 5.0V Iout < 3A fs = 400kHz – 3MHz

Development of Converter ASICs

Katja Klein 13Tracker Power System

• 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 pump in 130nm (CERN + external student) I = 60mA; developed for Atlas, but could also be used in CMS readout chips

Strip Tracker System Tests

Katja Klein 14Tracker Power System

• 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 + 30m shield--- Toroid converter + LDO--- T. converter + LDO + 30m shield

Total MB of: TEC modulesTEC Converters

• 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)

Simulation of Strip Material Budget

Katja Klein 15Tracker Power System

Original TECTEC with buck convertersr = 1/8

TEC electronics & cables: - 30.0%

• 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)

Tasks / Open Questions & Next Steps: Pixels

Katja Klein 16Tracker Power System

• 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)

Tasks / Open Questions & Next Steps: Strips

Katja Klein 17Tracker Power System

• 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

Tasks / Open Questions & Next Steps: Strips

Katja Klein 18Tracker Power System

• 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)

Summary & Conclusions

Katja Klein 19Tracker Power System

• 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

Back-up Slides

Katja Klein 20Tracker Power System

R&D Proposals relevant for Power WG

Katja Klein 21Tracker Power System

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

Open Tasks

Katja Klein 22Tracker Power System

• 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