Welcome 28.09.2011 Jan Sammet - 1 - C-DC converter based powering sc the upgrade of the CMS pixel det TWEPP-11, Wien 28.09.2011 Arndt Schultz von Dratzig, Lutz Feld, Waclaw Karpinski, Katja Klein, Jennifer Merz, Jan Sammet , Oliver Scheibling, Michael Wlochal
Welcome. A DC-DC converter based powering scheme for the upgrade of the CMS pixel detector TWEPP-11, Wien 28.09.2011 Arndt Schultz von Dratzig , Lutz Feld , Waclaw Karpinski , Katja Klein, Jennifer Merz , Jan Sammet , Oliver Scheibling , Michael Wlochal. Welcome. Outline. - PowerPoint PPT Presentation
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Welcome
28.09.2011 Jan Sammet - 1 -
A DC-DC converter based powering schemefor the upgrade of the CMS pixel detector
TWEPP-11, Wien28.09.2011
Arndt Schultz von Dratzig, Lutz Feld, Waclaw Karpinski, Katja Klein,
Jennifer Merz, Jan Sammet, Oliver Scheibling, Michael Wlochal
Welcome Outline
28.09.2011 Jan Sammet - 2 -
• Introduction
• Implementation into CMS
• Challenges…
• … and how we address them
• Conclusions & Outlook
WelcomeUpgrade of the CMS Pixel Detector
28.09.2011 Jan Sammet - 3 -
• CMS pixel detector is going to be replaced during shut down of LHC in ~2016 Additional layer of pixel modules
Number of readout chips (ROCs) increases by factor of 1.9 (16k 30k)
Present powering scheme cannot supply sufficient power through existing cables
Use DC-DC converters to reduce power losses
Aachen develops, tests and produces converters, to be used by CMS
93 cm
53 cm
The CMS pixel detector
Welcome Strategy
28.09.2011 Jan Sammet - 4 -
• Increase efficiency of power transmission
• Ploss=Rcable·I2
supply power at higher voltage r·U i.e. lower current I/r (Conversion ratio r >1)
power losses Ploss=R·(I/r)2 are reduced by factor r2!
DC-DC poweringModuleDC-DC
ModuleDC-DCPower suppy
Conventional poweringModule
ModulePower supply
How it works
• Frequently connect and disconnect source and load
• Duty cycle D = ton/T
• Conversion ratio r = Vin/Vout = 1/D (ideal converter)
Welcome DC-DC Buck Converters
28.09.2011 Jan Sammet - 5 -
• ASIC includes transistors and voltage regulation circuit
• ASIC is being developed within CERN electronics group (F. Faccio et al.) [see talk by S. Michelis http://indico.cern.ch/contributionDisplay.py?contribId=21&confId=120853]
• Radiation tolerance of many semi-conductor technologies evaluated AMIS I3T80 0.35µm (ON Semiconductor, US) - functional up to dose of 300Mrad & fluence of 51015 p/cm2
[F. Faccio, TWEPP-10, Development of custom radiation-tolerant DCDC converter ASICs]
Advantages
• Output regulation by pulse width modulation Vout is regulated
• Provide high currents with high efficiency
Welcome Aachen DC-DC Converter
28.09.2011 Jan Sammet - 6 -
PCB:2 copper layers a 35µm0.3mm thickLarge ground area on backside for cooling
Toroidal inductor:L = 450nHRDC = 40m
Shield/heat sinkA = 28 x 16 mm2
M 2.5g3.8% of a radiation length
“PIX_V7“:
Design guidelines from CERN grouphave been implemented.
Pi-filters at in- and output
ASIC prototype: AMIS2 by CERNIout < 3AVin < 12VVout configurable; (here: 2.5V & 3.3V)fs configurable, e.g. 1.3MHz
Welcome Challenges
28.09.2011 Jan Sammet - 7 -
• Ensure radiation tolerance of high voltage (~15V) power transistors
• Implement DC-DC converters into CMS
• Provide magnetic field tolerance air-core inductor risk of radiated noise
• Provide good shielding and cooling
• Provide high conversion efficiency
• Provide compact device with small impact on material budget
• Reduce and control noise emissions
(covered by CERN group)
Welcome Challenges
28.09.2011 Jan Sammet - 8 -
• Ensure radiation tolerance of high voltage (~15V) power transistors
• Implement DC-DC converters into CMS
• Provide magnetic field tolerance air-core inductor risk of radiated noise
• Provide good shielding and cooling
• Provide high conversion efficiency
• Provide compact device with small impact on material budget
• Reduce and control noise emissions
Welcome Implementation into CMS
28.09.2011 Jan Sammet - 9 -
2.2m
Mockup
Integration for pixel barrel onto supply tube
• Large distance of converters to pixel modules ( ~ 4) (goal is to be able to power detector, NOT to reduce material)
• CO2 cooling available
• 26 DC-DC converters per channel
• Power dissipation ~ 40W per channel
• Full channel (PCB, cooling pipes & bridges, 26 converters) weighs 200g and corresponds to 7% of a radiation length
• 2 000 DC-DC converters required in total
Pixel detector
Welcome Implementation into CMS
28.09.2011 Jan Sammet - 10 -
CAENA4603
PSU
PSU
Vana
Vdig
6 - 7 converters
1 - 4 pixel modules per converter
DC-DCdig
DC-DCana
6 - 7 converters
• Two CAEN power supply units (PSU) per supply tube channel• Power supplies need modification • I < 2.8A per converter (for L = 2 x 1034 cm-2 s-1)
Vout = 2.5V
Vout = 3.3V
Vin 12V
1 - 4 pixel modules per converter
50m
Welcome Challenges
28.09.2011 Jan Sammet - 11 -
• Ensure radiation tolerance of high voltage (~15V) power transistors
• Implement DC-DC converters into CMS
• Provide magnetic field tolerance air-core inductor risk of radiated noise
• Provide good shielding and cooling
• Provide high conversion efficiency
• Provide compact device with small impact on material budget
• Reduce and control noise emissions
Welcome Challenges
28.09.2011 Jan Sammet - 12 -
• Ensure radiation tolerance of high voltage (~15V) power transistors
• Implement DC-DC converters into CMS
• Provide magnetic field tolerance air-core inductor risk of radiated noise
• Provide good shielding and cooling
• Provide high conversion efficiency
• Provide compact device with small impact on material budget
• Reduce and control noise emissions
Electrical shielding:• Acts also as cooling contact for coil• Shape optimized to fit into edge channels of supply tube
Several technologies are under investigation:
• Hydroformed/deep drawn aluminium• Ruled out; required shape not feasible in mass production
• Plastic shields coated with a metal layer• Different materials, thicknesses and depositing
techniques have been tested
• Milled Aluminium shields• 120µm of Aluminium etched down to 90µm + 15 µm of Nickel
+ 15 µm of Copper
Welcome
28.09.2011 Jan Sammet - 13 -
R&D on Shielding
Welcome
28.09.2011 Jan Sammet - 14 -
Effectiveness of Shielding
• Measure z-component of magnetic field of DC-DC converter
• Automated x-y table allows high spatial resolution
• Many different materials and thickness have been tested focus on thinnest and lightest functional shieldings here
Scanning table
BZ
Welcome
28.09.2011 Jan Sammet - 15 -
Effectiveness of Shielding• 90µm milled Aluminium
• Magnetic field reduced to 15%• Price per piece ~ 25 €
• Plastic shield coated with 30 µm Cu• Magnetic field reduced to 30%• Price per piece: ~ 13 €
• Plastic shield coated with 60 µm Cu• Magnetic field reduced to 5%• Price per piece: ~ 13 €• Roughly 56% higher contribution to MB
No shield 90µm AL
60µm Cu
30µm Cu
offsetmean
noShieldmean
offsetmean
shieldmean
BBBB
Welcome
28.09.2011 Jan Sammet - 16 -
Thermal FE-Simulation• Cooling bridges clamp around CO2 pipes
• Chip cooled through PCB backside• Shield (soldered to PCB) acts as cooling contact for inductor
• Temperature of cooling bridge T = -20°C Chips are at -7°C (T = 13K) Coils are at -6°C ( T = 14K) For room temperature (20°C) operation, both stay below 40°C
-20
-10
-15
-6°C
Shielding simulated,but not displayed
0.5 1 1.5 2 2.5 30
20
40
60
80
100
120
60µm Cu.30µm Cu.Alu shieldingNo shielding
Welcome
28.09.2011 Jan Sammet - 17 -
Thermal Measurements
PIX_V7, 450nH, 1.3MHzVin = 10V, Vout = 3.3V
Output current [A]
Coi
l tem
pera
ture
[°C
]
• Converter on cooling bridge at 20°C Good agreement with Finite Element simulations Shielding fulfils task of cooling contact for coil Cooling of chips via backside of PCB is very effective
Welcome Challenges
28.09.2011 Jan Sammet - 18 -
• Ensure radiation tolerance of high voltage (~15V) power transistors
• Implement DC-DC converters into CMS
• Provide magnetic field tolerance air-core inductor risk of radiated noise
• Provide good shielding and cooling
• Provide high conversion efficiency
• Provide compact device with small impact on material budget
• Reduce and control noise emissions
Welcome Challenges
28.09.2011 Jan Sammet - 19 -
• Ensure radiation tolerance of high voltage (~15V) power transistors
• Implement DC-DC converters into CMS
• Provide magnetic field tolerance air-core inductor risk of radiated noise
• Provide good shielding and cooling
• Provide high conversion efficiency
• Provide compact device with small impact on material budget
• Reduce and control noise emissions
Welcome
Jan Sammet - 20 -
Efficiency
28.09.2011
• Phase 1 conditions: Vout = 3.3V or 2.5V, Iout < 2.8A, conversion ratio of 3-4 75% - 80% efficiency: ok – still expected to increase further with new version of AMIS chip
[White regions: regulation not working properly, Vout too low]
• System tests with original pixel PSU from CAEN and module qualification set-up• One full module (16 ROCs, each containing 4160 pixels) is read out• S-curve noise of each pixel is measured• Many thanks to PSI for hardware and advice
VA
Connectorboard
Moduleadapter
PC interface „Advanced Test Board“
DAQ PC Module
DC-DCconverter
s
CAEN Pixel PSU multi-service cables (40m)
VD
EASY4000
SY1527+ Branch
Controller
PSMA4603
Original pixel powersupply unit
HV(150V)
WelcomePowering with DC-DC Converters
28.09.2011 Jan Sammet - 27 -
• DC-DC converters cause no significant increase of noise
powering with DCDC
conventional powering
Welcome
28.09.2011 Jan Sammet - 28 -
Impact of Orbit Gaps• Orbit gaps of LHC beam no collisions for 3µs every 89µs Pixel digital current drops within 25..100ns (1..4 bunches, depending on the occupancy) Worst case for 2×1034cm-2s-1:
• ID_high = ~ 2.7A (86µs) ID_low = ~1A (3µs)
Stability Test of the whole power supply chain:
Also check impact of “inverted orbit gaps”
• ID_high = ~ 2.7A (3µs) ID_low = ~1A (86µs) (LHC fill with only a few intense bunches)
VA
Connectorboard
Moduleadapter
PC interface „Advanced Test Board“
DAQ PCModule
HV(150V)
DC-DCconverter
s
CAEN Pixel PS multi-service cables (40m)
VD
Dynamic Load Box
EASY4000
SY1527+ Branch
Controller
PSMA4603
ID
t
ID
t
Welcome Impact of Orbit Gaps
28.09.2011 Jan Sammet - 29 -
• Without DC-DC converters Load variations cause moderate increase of noise
• With DC-DC converters Sensitivity is reduced due to filtering components and regulation of DC-DC converter
Powering with DC-DC convertersConventional powering
WelcomeInfluence of the Switching Frequency
28.09.2011 Jan Sammet - 30 -
0.5 1.0 1.5 2.0 2.5 3.0 3.5123.5
124
124.5
125
125.5
126
126.5
127
Orbit gaps
2A add. load
Module only
Frequency [MHz]
Noi
se [e
]
Slight reduction ( < 1e ) at 2 MHz Not significant yet Might become relevant in larger system
é Not directly comparable to previous measurements
(slightly different cabling, no copper plate here)
0.5 1.0 1.5 2.0 2.5 3.0 3.50
50
100
150
Frequency [MHz]
Noi
se [e
]
Welcome Different Sensing Points
28.09.2011 Jan Sammet - 31 -
Dynamic Load
DC-DCconverter
CAEN PSmulti-service cables (40m) Module
Powering with DC-DC converters
Sensing at PS
Sensing at DC-DC converter
No increase of noise due to sensing at PS Sensing at DC-DC converters not necessary
• DC-DC converter is seen by PS as negative impedance Sensing at converter could cause instabilities Modifications of PS would be more complex and costly Measure influence of sensing point in system tests
Welcome Challenges
28.09.2011 Jan Sammet - 32 -
• Ensure radiation tolerance of high voltage (~15V) power transistors
• Implement DC-DC converters into CMS
• Provide magnetic field tolerance air-core inductor risk of radiated noise
• Provide good shielding and cooling
• Provide high conversion efficiency
• Provide compact device with small impact on material budget
• Reduce and control noise emissions
Welcome Conclusions & Outlook
28.09.2011 Jan Sammet - 33 -
Conclusions
• Good progress has been made towards a DC-DC converter based powering scheme
• Plans for implementation are far advanced
• Efficiency and noise performance of our DC-DC converters are satisfactory
Outlook
• Improve system tests with more modules, cold temperatures…
• Perform thermal cycling to simulate accelerated aging and to ensure reliable operation in the long term
• Implement new versions of the AMIS chip (AMIS4 expected soon)
• Implement control scheme for DC-DC converters
Welcome Back-Up Slides
28.09.2011 Jan Sammet - 34 -
Welcome The CMS Pixel Detector
28.09.2011 Jan Sammet - 35 -
• Pixel size: (100 x 150) µm²
Present barrel New barrel
Welcome Aachen DC-DC Converter
28.09.2011 Jan Sammet - 36 -
Design guidelines from CERN grouphave been followed.
Welcome
28.09.2011 Jan Sammet - 37 -
Mechanical & Thermal Integration
cooling pipes
lower part of cooling bridge
upper part of cooling bridge
chip area
• Cooling bridge clamps around pipe• Area reduced to reduce material• Aluminium (could be Graphite, but gain for material budget is low)
Welcome Effectiveness of Shielding
09.09.2011 Jan Sammet - 38 -
Welcome
28.09.2011 Jan Sammet - 39 -
Conductive Noise with Shielding
No shield Milled shield, 90µm Cu galvanic, 60µm Cu galvanic, 30µm0
2
4
6
8
10
12
14
16
18
20
DMCM
Qua
drati
c su
m o
f noi
se p
eaks
[dBµ
A]
Welcome Set-Up for System Tests
28.09.2011 Jan Sammet - 40 -
Original pixel powersupply system
Pixel module
DC-DCconverters
WelcomePowering with DC-DC Converters 2
28.09.2011 Jan Sammet - 41 -
• Variations with different but identical converters ~2e
• Reproducibility of measurements ~1e
VD = 3.2V, VA= 2.5V
VD = 3.2V, VA= 2.5V
WelcomeInfluence of the Switching Frequency
28.09.2011 Jan Sammet - 42 -
With inverted orbit gaps With simulated orbit gaps