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Implementation of DC-DC Converters into the CMS Tracker at Super-LHC . Katja Klein 1. Physikalisches Institut B RWTH Aachen University. ATLAS / CMS Power Working Group CERN, March 31st, 2010. Outline. DC-DC converters for CMS phase-1 pixel upgrade CMS track trigger layers - PowerPoint PPT Presentation
Citation preview
Implementation of DC-DC Converters intothe CMS Tracker at Super-LHC
ATLAS / CMS Power Working GroupCERN, March 31st, 2010
Katja Klein1. Physikalisches Institut BRWTH Aachen University
Outline
Katja Klein 2DC-DC Conversion for CMS Tracker Upgrade
DC-DC converters for• CMS phase-1 pixel upgrade• CMS track trigger layers• CMS outer tracker upgrade
Caveat:can present only a snap shot of current ideas; outcome of Chamonix Workshop and consequences are still being discussed...
Powering the CMS Tracker Upgrade
Katja Klein 3DC-DC Conversion for CMS Tracker Upgrade
In 2008 a task force, led by Peter Sharp, was set up to look into the two options: Serial Powering and DC-DC conversion.
As a result of this review process, the CMS tracker has chosen DC-DC conversion as baseline solution, and maintains Serial Powering as back-up (January 2009).
Reasons:- closer to today‘s parallel powering scheme (modularity, failure modes,
grounding & shielding, ...)- only one new component required (the DC-DC converter)- less consequences on system design (classical grounding, no AC-coupling etc.)
CMS Pixel UpgradeThe easy application
Katja Klein 4DC-DC Conversion for CMS Tracker Upgrade
Phase-1 Pixel Upgrade
Katja Klein 5DC-DC Conversion for CMS Tracker Upgrade
BPIX: 3 barrel layers 4 layers r = 3.9, 6.8, 10.9, 16.0cm
FPIX: 2 x 2 disks 2 x 3 (larger) disks(3rd disk had been staged)
• Number of ROCs increases: BPIX: 11 520 19 456; FPIX: 4 320 10 756• Modifications to PSI46 ROC to reduce data losses (buffer size ...)• Reduction of material (light-weight mechanics, CO2 cooling ...)• DC-DC conversion... more radical changes are under discussion
Current pixel detector:
Cell size: 100µm x 150µm
Pixel Power System
Katja Klein 6Pixel PowerSystem Developments
• PSI46 ROC needs two supply voltages: Vana 1.5V and Vdig 2.5V• On-chip voltage regulators compensate for differences in supply voltage due
to voltage drops on cables, and improve power noise rejection• Supplied by 56 CAEN A4603 power supply modules (EASY 4000 system)
- Want to keep power supplies, if possible (perhaps with light modifications)
• 40m + 5m long multi-service cables to pixel supply tube – cannot be exchanged• Cables run along supply tube to pixel detector
pixel det.
Why DC-DC Converters?
Katja Klein 7Pixel PowerSystem Developments
• More readout chips per cable and per power supply• FPIX: might cope without DC-DC converters (cables for 3rd disk already installed)
• BPIX: - Increase of heat load in cable channels by a factor of 3- Required power cannot be delivered by todays’ power suppliesÞ Need to reduce supply currents and thus power losses in supply cablesÞ Decision in June 09 to go for buck converters, located on far end of supply tube
- Low conversion ratio (~ 2:1) to be compatible with voltage specification of PS
• Note: DC-DC converters needed even if PS would be replaced, to reduce heat load in cable channels
DC-DC Converters: BPIX Scheme
Katja Klein 8Pixel PowerSystem Developments
A4603PSU
PSU
Vana
Vdig
4-5 converters 4 barrel modules per converter
DC-DCdigital
DC-DCanalog
4-5 converters
FPIX: 2 blades per DC-DC converter
4 barrel modules per converter
Converter Integration - BPIX
Katja Klein 9Pixel PowerSystem Developments
• Multiservice cables arrive at point 0• PCB with DC-DC converters in region 1• Embedded standard cables in region 2• PCB in region 3 & thin wires to modules at 4
Mock-up in preparation
0
2
3
4
Silvan Streuli, 28/10/2009
1
Pixel PowerSystem Developments 10
“Specs“ for Pixel DC-DC Converters (I)
Katja Klein
Numbers are still subject to changes.
Converter type: Inductor-based non-isolated step-down converter, probably of buck-type, integrated on a separate PCB.
Conversion ratio Vin/Vout: 2 - 3
Output voltage Vout: Vana = 2.3V Vdig = 3.5V
Input voltage Vin (for 1:2): Vana = 4.6VVdig = 7.0V
Output current Iout: < 2.8A (in some detector regions up to 4.9A – adapt modularity?)
Switching frequency: 1 - 2 MHz Low frequency to maximize the efficiency.
Efficiency: 80%
Pixel PowerSystem Developments 11
“Specs“ for Pixel DC-DC Converters (II)
Katja Klein
Dissipated power: 2-3W per converter for 80% efficiency. Active cooling has to be foreseen.
Dimensions of PCB: Length = 3.2cm , width = 2cm, height <1.4cmSmall piggy-board with board-to-board connectors
Material budget / Weight: Since these converters are at z = 2.0-2.3m and r ~ 19cm they are absolutely outside of the tracking region and therefore uncritical in mass and material budget. The only concern is the use of material with little activation.
Output voltage ripple: Since the PSI46 ROC has rather fast on-chip regulators, the requirements for ripple are very relaxed.
Radiation environment: 19cm radius, z = 2.3m, 700fb-1, safety factor = 2: Fast hadrons fluence: 6-7 x 1014 /cm2
Dose: 200kGy
Specific requirements: Behaviour for very fast load variations due to orbit gaps. Stability of operation together with long pixel cables and the CAEN A4603 power supply modules.
Prototype: AC_PIX_V4 Buck Converter
Katja Klein 12Pixel PowerSystem Developments
Chip: AMIS2 by CERNVIN < 12VIOUT < 3AVOUT = 3.3VfS ≈ 1.3MHz
PCB:2 copper layers a 35mFR4 1mmA = 18mm x 25mm for QFN32
Input and output π-filtersL = 12.1nH, C = 22µF
Air-core toroid:Custom-made toroid, 6mm,height = 7mm, L = 600nH, RDC = 80mΩ
25mm18
mm
m = 2.7g
Cooling contact
AC_PIX_V4 Efficiency
Katja Klein 13Pixel PowerSystem Developments
0.0 0.5 1.0 1.5 2.0 2.5 3.050
55
60
65
70Vin=10V, Vout = 1.2V, Iout =1A
Frequency [MHz]
Effic
ienc
y [%
]
• ~ 75% for 3A and conv. ratio of 2-3• Res. losses (Ron, wire bonds, coil ) ~ 1/fs;
switching & driving losses ~ fs
• Further improvements are expected: Move from 1.3MHz to 1.0MHz Gain few % with cooling Move to flip-chip package On-chip routing? PCB layout, capacitors etc.?
PIX_V4, Vout = 3.3V, f = 1.3MHz
0.00 10.00 20.00 30.00 40.00 50.00 60.00 70.00 80.000.69
0.70
0.71
0.72
0.73
Vin = 10V, Vout = 3.3V, Iout = 2.8A
Chip package temperature [°C]
Effic
ienc
y [%
]
AC_PIX_V4 Noise Behaviour
Katja Klein 14Pixel PowerSystem Developments
Vin = 10V, Vout = 3.3V, Iout = 1.4A, fs = 1.3MHz
Differential Mode
Common Mode
L = 12.5nHC = 22µF fcut 600kHz
• On-board pi-filter Þ DM noise reduced wrt. CM• However, performance of filter to be improved• Recall: PSI46 has Linear Regulators• Tests with real pixel modules in preparation for
FPIX (Fermilab) and BPIX (Aachen)
Enpirion withexternal pi-filter
System Aspects
Katja Klein 15Pixel PowerSystem Developments
• Operation with 40m long cables and A4603 CAEN power supplies• Remote sensing of CAEN power supplies at input of DC-DC converters• Stability of Vout (both from converter & CAEN PS) during fast load variations
on digital line- Digital activity lower during orbit gaps (3µs)- Idig = 2.7A 1.9A for L = 21034/cm2/s
- Changes within one to few bunch crossings- Current supplied by capacitors on pixel module?
• System test activities & simulations started (FNAL, Aachen)
CMS Track Trigger LayersThe most demanding application
Katja Klein 16DC-DC Conversion for CMS Tracker Upgrade
Track Trigger Layers
Katja Klein 17DC-DC Conversion for CMS Tracker Upgrade
α
J. Jones (~2005)CMS Tracker SLHC Upgrade Workshops
• Tracking information needed in L1 trigger, to preserve trigger rate at nominal value• All ideas based on discrimination between low and high pT tracks due to bending
- Cluster width approach OR stacked, closely spaced, pixelated layers• Worst case in terms of power consumption: “Long Barrel Double Stack“ layout
Þ whole tracker constructed out of double-stacked layers (~ 300m2)
The “Long Barrel Double Stack“ layout
4 layers
Track Trigger Power Requirements
Katja Klein 18DC-DC Conversion for CMS Tracker Upgrade
Estimates for stacked layers FE power consumption from CMS:• Power/channel: 0.1mW for 100µm x ~2mm pixel• Power per unit area: ~100mW/cm2
• Power per double module: 2W – 9W
More relevant: supply currents• 130nm or 90nm technology: 1.2V (analogue) or 0.9V (digital)• Total current at 1.2V: 1.6 ... 8A. Note: buck supply current 3-4A.• Digital power consumption ~ 50-75% of total; lowering Vdig to 0.9V halfes Pdig
Need up to 2 x 2A at 1.2V and 2 x 2A at 0.9V per double module
Þ Two buck converters (1 x 1.2V, 1 x 0.9V) per double module- Currents at 0.9V too large for switched capacitors- Linear regulator for 0.9V: efficiency = 0.75%
Link Power Requirements
Katja Klein 19DC-DC Conversion for CMS Tracker Upgrade
• Power per GBT link: 2W• Power per pixel (50% usage of bandwidth): 150µW• 1 GBT per double module for trigger data: 2W• Separate GBT links for readout
• GBTIA, GB Laser Driver: 280mA at 2.5V• GBTX: 1.0A at 1.5V
Various options:1) One buck (1.5V) plus one step-up switched capacitor conv. (2.5V) per GBT2) As 1), but 1.5V buck converter delivers in addition Vana to module (25% more P)
3) Two buck converters (1.5V, 2.5V) per 1-3 GBT(s)
P. Moreira, GBTX SPECIFICATIONS V1.2
Requirements for CMS Stacked Layers
Katja Klein 20DC-DC Conversion for CMS Tracker Upgrade
Quantity Requirement CommentsRadiation level Fast hadron fluence: ~9x1015/cm2;
Dose: ~1.3MGyFor R > 20cm, z < 3m, 5000fb-1, safety factor of 2
Output voltage Vana = 1.2VVdig = 0.9V
Assuming 130 or 90nm(+ Vopto = 2.5V, 1.5V)
Output current 3-5A 2 converters per double module
Conversion ratio Up to 10:1, depends on proposal Max. current in cable channels 15kAAssuming ~100kW & 80% efficiency
Efficiency 70-80% Losses need to be cooled
Conductive noise(DM, ripple)
Depends on PSRR of the ROC (still to be studied);but fs well below (or ideally above) system susceptibilty, i.e. ~ 1MHz
Can be filtered
Common mode noise ? As low as possible... Notoriously hard to control
Radiated noise(magnetic near field)
Ideally none Minimize with distance, shielding, module design
Material budget Critical since installed at low R Expect 1-2g per converter
Real estate No space on FE-hybrid 2-4cm2 per converter must be found
Prototypes: AC_AMIS2 and AC2
Katja Klein 21DC-DC Conversion for CMS Tracker Upgrade
Chip: AMIS2 by CERN (QFN48)VIN = 3 - 12VIOUT < 3AVOUT = 1.2V (also 2.5V)fS ≈ 1.3MHz (V1) or programmable (V2)
Input and output π-filtersL = 12.1nH, C = 22µF
25mm
19m
m
Air-core toroid (both converters): 6mm, height = 7mm, L = 600nH, RDC = 80mΩ
19mm
12mm
m = 1.1g Chip: Enpirion EQ5382DVin = 2.4-5.5V(rec.)/7.0V(max.)Iout 0.8Afs 4MHz
Standard filters (C1||C2)
Power Efficiency Pout/Pin
Katja Klein 22DC-DC Conversion for CMS Tracker Upgrade
Enpirion chip, Vout = 1.3V
• Efficiency drops with conversion ratio and current• Efficiency not yet sufficient• Ohmic losses in transistor, wire bonds, PCB, coil; switching losses etc.• Improvements possible, but need to be careful not to add more material...
AMIS2, Vout = 1.2V, fs = 1.3MHz
Noise
Katja Klein 23DC-DC Conversion for CMS Tracker Upgrade
• Noise of prototypes has been studied in system test with current strip modules
Þ Noise increases with conversion ratio Þ Noise increases for lower switching frequency (as required for efficiency)• Further R&D required to make noise emissions compatible with trigger layers
1 1( ) outin out
in
VI V V
V fs L -
1 1U I ESR Ifs C
• AMIS2 (QFN32) with input & output pi-filter: 25mm x 18mm... but LDO for 3.3V and some passives will vanish • Enpirion converter: 19mm x 12mm ... but pi-filter at output desirable• Height ~ 10mm, dominated by inductor (to be optimized)
Þ Final size will be inbetweenÞ Will be hard to squeeze below 2cm2 without compromising performanceÞ Trade-off between redundancy and size (e.g. input pi-filter)
If two converters (1.2V/0.9V) needed per double module:• can of course be installed on one PCB• size increases by a factor of 1.5
Space Requirements
Katja Klein 24DC-DC Conversion for CMS Tracker Upgrade
25mm
18m
m
Space Requirements
Katja Klein 25DC-DC Conversion for CMS Tracker Upgrade
80mm
26mm
Enpirion converter, to scale
pT-module by Geoff Hall et al.
pT-module by Sandro Marchioro
A Possible Implementation
Katja Klein 26DC-DC Conversion for CMS Tracker Upgrade
Converters could be integrated into support structure: no space on hybrid required height/shape of coil no issue larger distance less magnetic field easier shielding (e.g. by existing Carbon Fibre structures) much easier cooling Kapton bus between converter and modules - needed anyway: GBT, by-pass caps decoupling of module & converter R&D, QA etc. straight-forward in double-stack proposal (less obvious in others)
20cm
Per 100cm2 double-module:1 GBT 1 DC-DC a 1.2V for module power1 DC-DC a 0.9V for module power1 DC-DC a 1.5V for GBT1 DC-DC a 2.5V for GBT
Þ 2 PCBs a 4cm2 ~ ok
100cm2 1 PCB
1 PCB
A lot of space inside – is it usable?
Marvin Johnson, CMS Upgrade WS, 2009
CMS Outer Tracker UpgradeThe classical application
Katja Klein 27DC-DC Conversion for CMS Tracker Upgrade
Upgrade of the CMS Tracker for SLHC 28
Outer Tracker Upgrade
Katja Klein
• Some proposals combine a minimalistic trigger configuration with a “classical“ outer strip tracker
• Successor of APV25, the CMS Binary Chip (CBC), foreseen as readout ASIC (under development)
• 1 CBC (128 channels) needs P = 64mW (for 1.2V supply voltage)
Two stacked trigger layersR = 25cm & 35cm27m2 active area12kW FE-power (0.1mW/pixel)
Tracking layers2.5/5.0cm strips85m2 active area10kW FE-power(0.5mW/strip)double-sided
single-sided
z [cm]
R [c
m]
Pixel
DC-DC Converters for Outer Tracker
Katja Klein 29DC-DC Conversion for CMS Tracker Upgrade
• Power requirements: only 1.5W per module• Idea: use 1.2V buck converter (requ. conv. ratio ~ 4)
plus maybe on-chip charge pump (currents are low)• Space is again tight – various ideas:
- move into 3rd dimension- integrate into support structure
• Tests have to wait for CBC and module prototypes
Top Bottom
sensor
CBC
cooling block TPG stripshybrid
DC-DC converter
Summary
Katja Klein 30DC-DC Conversion for CMS Tracker Upgrade
• Earliest and best understood application: pixel detector at “phase-1“• Some noise tolerable, due to on-chip regulators• Space and mass not so critical ( 4)
• Most demanding and most speculative application: stacked layers for trigger • Large currents at high conversion ratio with high efficiency required• No space available and material budget very critical
• Converters for trigger layers probably also fine for Outer Tracker layers• On-chip charge pump is an option to be explored • After Chamonix workshop upgrade plans need to be refined, but R&D on
DC-DC conversion will for sure stay on the agenda
Back-up Slides
Katja Klein 31DC-DC Conversion for CMS Tracker Upgrade
AC_AMIS2 Schematics
Katja Klein 32DC-DC Conversion for CMS Tracker Upgrade
W. Karpinski, I. Özen (RWTH Aachen)
On-Chip Common Mode Subtraction• 128 APV inverter stages powered from 2.5V via common resistor (historical reasons)
Þ mean common mode (CM) of all 128 channels is effectively subtracted on-chip • Works fine for regular channels which see mean CM• CM appears on open channels which see less CM than regular channels• CM imperfectly subtracted for channels with increased noise, i.e. edge channels
Katja Klein 33DC-DC Conversion for CMS Tracker Upgrade
inverter
V125V250
VSS
V250R (external)
vIN+vCM
vCM
vOUT = -vIN
Node is common to all 128 inverters in chip
pre-amplifier
strip
V125
V250
VSS=GND
APV25 pre-amplifier
[Mark Raymond]
Katja Klein DC-DC Conversion for CMS Tracker Upgrade 34
Module Edge Strips
bias ring
[Hybrid]
strip
• Edge strips are capacitively coupled to bias ring• Bias ring is AC coupled to ground• Pre-amplifier is referenced to 1.25V• If V125 is noisy, pre-amp reference voltage
fluctuates against input• This leads to increased noise on edge channels
Material Budget (MB)
Katja Klein 35DC-DC Conversion for CMS Tracker Upgrade
Motivation for new powering schemes is to save material inside the tracker
ChipC‘s & R‘s ToroidCopper layersConnectorFR4 of PCB
Without DC-DCWith DC-DC- 30.9%
MB of electronics & cables
• Detailed study of Enpirion-converter, 1 per Tracker End Cap module, located on FE-hybrid• Assumptions: 80% efficiency, r = 8, Iout = 2A per module, Uout = 1.2V• Simulation of current tracker layout with CMS software based on GEANT4
Þ Converter adds 10% of strip module, but still saves 30% in electronics & cables MB of End Cap buck converters