Novel Powering Schemes for the CMS Tracker Upgrade - R&D at RWTH Aachen University

Novel Powering Schemes for the CMS Tracker Upgrade -

R&D at RWTH Aachen University

Meeting of the Joint Atlas/CMS Powering WG7th of April, 2008

Lutz Feld, Rüdiger Jussen, Waclaw Karpinski, Katja Klein, Jennifer Merz, Jan Sammet

1. Physikalisches Institut B, RWTH Aachen University

CMS tracker R&D on novel powering schemes at RWTH Aachen University 2

• The current CMS tracker and its powering scheme• Plans for R&D at RWTH Aachen University• System test with commercial DC-DC converters

– The converter– Setup and methodology – First preliminary results

• Summary & Outlook

Katja Klein

Outline

CMS tracker R&D on novel powering schemes at RWTH Aachen University 3Katja Klein

The Current CMS Tracker

2.5 m

5.8 m

Pure silicon tracker: 1m2 pixel area + 200m2 strip area 15 148 silicon strip modules, 29 different types 10 Million Strips, 84 Million pixels Operating temperature < -10 C


The Current CMS Tracker

Frontend-Hybrid with - 4 or 6 APV25 readout chips - PLL chip for timing - Multiplexer chip (MUX) - DCU chip for control

APV25 readout chip: - 0.25 m CMOS - 128 strips per APV - analogue readout - per channel: pre-amplifier, CR-RC shaper, 4 s pipeline - = 50ns

Typical strip module

• Supply voltages: 1.25V & 2.5V for analogue readout and 2.5V for digital control ring• Currents per APV: 0.118A at 2.5V and 0.061A at 1.25V• Power consumption of 4 (6) APV module including optical conversion: 1.8W (2.7W)


Powering the Current CMS Tracker

• Total strip tracker FE power consumption: 33kW• Total power supplied to strip tracker: 68kW 34kW = 50% is lost in the cables• Inside cold volume, 36% is lost in the cables

• Several modules (typically 8) are powered in parallel• Custom CAEN power supply system (EASY 4000) - A3486 AC/DC converter provides 48VDC - A4601/4602 provide 2.5V, 1.25V & bias voltage• Copper low impedance cables from racks to patch panel just outside of tracker volume ( 50m) • Aluminium or copper multiservice cables from patch panel to tracker structures (few metres)

Patch panel


• Significant R&D effort started slowly due to ongoing work for current tracker• Strawman tracker designs are being worked out• Main focus of current R&D on simulation of strawmen• A new big challenge: integration of tracker into Level1 trigger• Re-design of readout chip has not yet started

future chip parameters not known all system tests on powering schemes still have to be done with APV25

• Boundary conditions for powering to be understood - must current cables be re-used?

• Serious thinking on powering schemes has started about half a year ago; no prejudice for serial powering or DC-DC conversion

• Tracker power working group is being set up

Katja Klein

CMS Tracker R&D for SLHC


• Lutz Feld: team leader• Waclaw Karpinski (+ workshop team): electronics engineer• Katja Klein: HGF Fellow (4 years)• Three diploma students:

– Jan Sammet: System test measurements with DC-DC converters– Rüdiger Jussen: Development and test of radiation hard magnetic field

tolerant DC-DC converter (in collaboration with CERN PH-ESE group, see later)

– Jennifer Merz: Simulation of material budget of various powering schemes

Katja Klein

Working Group at RWTH Aachen University


• No prejudice wrt serial powering and DC-DC conversion investigate and learn about both schemes before decision can be taken

• DC-DC conversion started– Contributions to the development of a rad. hard, magnetic field tolerant buck

converter (development of PCB), in coll. with CERN PH-ESE (F. Faccio et al.)– Characterization of this custom converter: magnetic field test, irradiation tests– Integration into and system test with current & future tracker structures– Preparation of setups & first system tests with of-the-shelf converter ongoing– In the longer term: study of general system issues

• 1-step or 2-step conversion?• Converter on chip/hybrid/PCB?• Interplay with new readout chip etc.

• Serial powering not started yet– Integration of serial powering scheme into current/future tracker system– System performance test

• R&D proposal submitted and approved (Dec.) within CMS

Katja Klein

Plans for R&D at Aachen


A Commercial DC-DC Converter

Market survey (W. Karpinski) with main criteria: - high switching frequency small size of passive components - high conversion factor - sufficient current (~ 1A) & suitable output voltages (1.25V and 2.5V) Enpirion EN5312QI (studied) and Micrel MIC3385 (delivered recently)

Characteristics of EN5312QI:• Small footprint: 5mm x 4mm x 1.1mm• fs 4 MHz• Vin = 2.4V – 5.5V (rec.) / 7.0V (max.)• Iout = 1A• Integrated planar inductor with iron-manganese-zinc core

Custom rad. hard converter under development, delivery expected for summer start with a commercial of-the-shelf converter to prepare setups, to learn about

system behaviour and to gain experience


Integration into CMS End Cap System

• 4-layer adapter PCB• Plugged between Tracker End Cap (TEC) motherboard and FE-hybrid• 2 converters provide 1.25V and 2.5V for FE-hybrid• Input and output filter capacitors on-board• Input power external or via TEC motherboard


Integration into CMS End Cap System

Front-end hybrid

L-type:Larger flat PCB,1 piece

TEC motherboard(„InterConnect Board“, ICB)

S-type:Smaller inclined PCB, 2 pieces


EN5312QI: Inductor & Magnetic Field Tolerance

• MEMS technology: spiral inductor betw. magnetic cores• Decrease of efficiency in magnetic field• Total breakdown for fields below 1T (no surprise)• Lower magnetic field tolerance for higher duty cycles D D = Ton / T = Vout / Vin • Tolerance depends on orientation of converter in field

magnet (B < 1.2T)

Vout = 1.25VAxial:Tangential:

B-probe

X-ray, U = 35kV, 5 minutes


EN5312QI: EMI Measurements

• Standardized EMI test setup at CERN (details in talk by G. Blanchot)• Standalone test of converter noise (common & differential mode)• Different converters and PCB designs can be compared• Low noise emission of EN5312QI (only S type measured)• Duplication of setup in Aachen has started

Common modeDifferential mode

Load

EMI receiver

Filters

Current probe

EMI Setup at CERN


System Test Setup• TEC “petal“ with InterConnect Board• Four ring-6 modules powered & read out• Petal housed in grounded metall box• Optical readout• Optical control communication• Thermally stabilized at +15°C• Final components (spares)• Official DAQ software

6.16.4 6.3 6.2


Effect of Converter (Position 6.4)

Pos. 6.4

Pos. 6.4

---- No converter---- L type---- S type

Powered via ICB

Prel

imin

ary

Prel

imin

ary

Raw noise increases by 5-10% Design of PCB has significant impact Further optimization seems possible


Effect of Converter (Position 6.4)

Pos. 6.4

Pos. 6.4


Powered via ICB

Prel

imin

ary

Prel

imin

ary

Broader common mode distribution Huge increase of noise at module edges, APV edges and “bad“ strips effect is not yet understood


Effect of Converter (Different Positions)

Pos. 6.2

Pos. 6.3 Pos. 6.4


(Comparison for position 6.1 not possible because L type does not fit)

Powered via ICB

Prel

imin

ary

Prel

imin

ary

Prel

imin

ary


Common Mode Subtraction---- Raw noise without converter---- Raw noise with converter---- CM calculated per APV (128 strips)---- CM calculated for 32 strips---- Linear CM subtraction

L Type Powered externally

Pos. 6.4L type

Prel

imin

ary

Additional noise completely subtractable with proper common mode algorithm Noise increase due to higher common mode


Cross Talk

L TypePowered externally

Pos. 6.4L type

Pos. 6.3

---- No converter---- Converter on all positions---- Converter on 6.4 only

---- No converter---- Converter on 6.4

Prel

imin

ary

Prel

imin

ary

Performance with converter does not depend on # of modules operated with converter A converter on position 6.4 does not spoil the performance of modules without converter (e.g. 6.3)


Cross Talk

Pos. 6.3

Pos. 6.4

Strip number Strip number

Cor

rela

tion

coef

ficie

nt

Cor

rela

tion

coef

ficie

nt

PreliminaryPreliminary

Study correlations between pairs of strips i, j (R = raw data):Corrij = (<RiRj> - <Ri><Rj>) / (ij)

No cross-talk between neighbouring modules observed High correlations only within single modules (common mode)

With converters on 6.3 and 6.4Without converters

Strip

num

ber

Strip

num

ber


Noise versus Input Voltage

Pos. 6.4L type

Pos. 6.4L type

Prel

imin

ary

Mean noise increases with input voltage or conversion ratio g (g = Vin / Vout)

2 2

1 1 1 1(1 ) 116 16

outout in

out s out out s

VV D D V DLC f V LC f

Expectation for output voltage ripple Vout (with duty cycle D = Vout / Vin):

Mean noise per module

Prel

imin

ary


• We have started to a programm to understand the issues related to operation of CMS tracker modules with DC-DC converters

• First measurements with a commercial converter indicate an increase ofthe module noise due to a higher common mode by up to 10%

• Increase of edge strip noise to be studied • Further optimization of adapter PCB seems possible• No indication for cross talk when powering with DC-DC converters• Many more interesting measurements are in the pipeline

– Operation of a complete petal with Enpirion converters– Noise injection on silicon modules– Micrel converter with 8 MHz switching frequency– Integration of EN5312QI with external air coil– Combination of DC-DC converter with voltage regulator

• Hope to start similar studies with custom converter (CERN) this summer

Katja Klein

Summary & Outlook

Back-up


Different Methods of Powering

Pos. 6.4L type

Pos. 6.4S type

---- No converter---- L/S type powered externally---- L/S type powered via ICB; many filter capacitors

Prel

imin

ary

Prel

imin

ary

Sensitivity to input voltage ripple to be strudied, but sensitivity seems to be small


Effect of Output Filter Capacitance

Powered externally

Pos. 6.4L type

Pos. 6.4S type

---- No converter---- Standard output filter capacitors---- Additional 22 F capacitor---- Additional 100 F capacitor

Prel

imin

ary

Prel

imin

ary

Noise can be reduced further by larger output filter capacitances

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Novel Powering Schemes for the CMS Tracker Upgrade - R&D at RWTH Aachen University