Transcript Folie 1 - RWTH Aachen University

Noise Susceptibility Studies /
Magnetic Field Tests Status & Plans of the Aachen Group
Lutz Feld, Rüdiger Jussen, Waclaw Karpinski,
Katja Klein, Jennifer Merz, Jan Sammet
1. Physikalisches Institut B, RWTH Aachen University
Tracker Upgrade Power WG Meeting
June 4th, 2009
Outline
• Personal & funding
• Noise susceptibility studies
• Magnetic field test of DC-DC converters
• Plans
• Summary
Katja Klein
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Update on Personal
• Lutz Feld: team leader
• Waclaw Karpinski: electronics engineer
– plus electronics workshop team
• Katja Klein: Helmholtz Alliance fellow (4-years from April 08)
• Two PhD students:
– Jan Sammet
– Rüdiger Jussen
• Diploma student:
– Jennifer Merz (Effect of powering schemes on the material budget)
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Funding News
We have received from BMBF (= main German funding body for HE physics)
for the next 3-year funding period, starting July 09:
 invest money
 3 PhD positions for SLHC
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Summary of Activities
• Investigation of system aspects of novel powering schemes
– PCB development & system tests  separate talk today by Jan Sammet
• Noise susceptibility measurements
– Noise injection into silicon strip modules  covered in this talk
• Contribute to the development & characterization of magnetic field
tolerant and radiation hard DC-DC buck converters, in coll. with CERN
PH-ESE group
– Magnetic field test  covered in this talk
– Integration and test of CERN converters with CMS strip modules
 only short summary of plans today
• Simulation of material budget of different powering schemes
 final results ready, will be presented in the next meeting
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Noise Susceptibility Studies
• Goal: identify particularly critical bandwidth(s) for converter switching frequency
• Bulk current injection (BCI) test-stand has been set up (Rüdiger Jussen)
• A noise current of 70dBA (Ieff = 3.16mA) is injected into the power lines
 Differential Mode (DM) and Common Mode (CM) on 2.5V and 1.25V
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BCI Set-up
Injection & current probe
LISN
Current probe in CM configuration
Petal
Frequency
generator
Power
supplies
Amplifier
Spectrum analyzer
Noise injection into one
module (6.4)
• Noise is injected into a single module
• Frequency swept from 100kHz – 100MHz
• Step width: 0.1MHz between 100kHz and 10MHz,
1.0MHz between 10MHz and 30MHz,
2.5MHz between 30MHz and 100MHz
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Effects on Module Noise
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Effects on Module Noise
Mean noise of APV2
Noise of strip 512
• Edge strips much more sensitive due to
their coupling to the bias ring
• On-chip common mode subtraction is very
efficient for most strips
• More in back-up slides
 Concentrate on edge strips
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Peak Mode
• Peak at 6-8MHz, not at 1/(250ns) = 3.2MHz, as expected from shaping time
• Higher susceptibility for differential mode and 1.25V = pre-amp reference voltage
• Peak position independent of injected amplitude or module position
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Peak vs. Deconvolution Mode
Deconvolution mode
Peak mode
• Slight shift of peaks
• Interpretation difficult
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What about Higher Frequencies?
Zoom
• Cable resonances can be observed if cable length L = n/4
• Two open ends (LISN 50, module ~ 2)  L = /2
• Cable length varied between ~ 1.1m, 1.5m, 2.1m  f = 89.8MHz, 65.9MHz, 47.0MHz
• Measurements above ~ 30MHz are not reliable
• But no shift of peaks below 30MHz
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Influence of Pre-amp Reference Voltage
APV25 pre-amplifier
DM, 2.5V
V250
V125
strip
bias ring
VSS=GND
[Mark
Raymond]
connected
connect toto
Ground
V125
[Hybrid]
Katja Klein
• Edge strips are capacitively coupled to bias ring
• Bias ring referenced to ground, pre-amp to 1.25V
• Bias ring connected to 1.25V instead of ground
 Susceptibility decreases drastically
 Pre-amp should be referenced to ground
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BCI Summary
• Results are ~ consistent with measurements of Fernando Arteche (2004)
• Powerful method, but interpretation difficult (needs modelling)
• Shorter measurement time needed for faster turnaround (now ~ 1d per curve)
 automation of measurement with LabView is foreseen (Rüdiger)
• Will be useful to characterize susceptibility of SLHC devices (hybrids, modules, ...)
F. Arteche, measurements with
TEC petal in Aachen, 2004
(SLAC-PUB-11886, May 2006 )
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Magnet Test
• DC-DC converters must function in ~ 4T magnetic field  no magnetic components
• Tests with 7T NMR-magnet at Forschungszentrum Jülich, close to Aachen
• Enpirion and CERN AMIS1 buck converters + LBNL charge pump tested (Rüdiger)
 both versions with air-core and ferrite coils
 13 DC-DC converters tested in total (can show only examples here)
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Magnet Test Set-up
B field
Handle for probes
9m long BNC cables
Sourcemeter
= Load
Handle being inserted into magnet
Magnet
Scope with
probes
PS
Windows-PC
running LabView
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Efficiency Measurement
Regulated by converter
Value set in sourcemeter
and monitored with current probe
Vout  Iout
Eff 
Vin  Iin  R  Iin 2
Set and measured
with PS
Measured with PS
Correction for cable losses
• Note: the output voltage was not measured  this must be changed in the future!
• Efficiency was measured inside and outside of magnet with same set-up
• Measurement of other observables (ripple?) difficult due to long cables
 what else should be measured?
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Efficiency (7T) / Efficiency (0T)
Enpirion EQ5382D Buck Converter
Enpirion with ferrite coil
Vout = 1.25V
Katja Klein
• Severe efficiency loss with ferrite inductor
• Efficiency change < 0.5% with air-core inductor
Enpirion with air-core toroid
Eff. (7T) / Eff. (0T)
Vout = 1.25V
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AMIS1 Buck Converter w/ Air-Core Solenoid
Efficiency (7T) / Efficiency (0T)
• Efficiency changes by less than 5% with air-core inductor
• Reason for larger deviations wrt Enpirion not clear, converter stability?
• With ferrite inductor, PS went in over-current condition (back-up slides)
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LBNL Charge Pump
• No efficiency change for Vout = 2.5V
• For Vout = 1.25V, converter was probably not in same “state“ (stability problems)
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Magnet Test Summary
• No surprises:
 All converters with ferrite coils showed severe efficiency loss or over-current
 All converters with air-core inductors, plus charge pumps, worked without
significant efficiency loss
• We know now how to do the measurements and what to improve
 Measure output voltage
 Test various coil orientations
• Time needed for a measurement campaign: 2 days (but must be arranged)
• Suggest to repeat test with CERN ASIC in IHP technology and improved set-up
 maybe also with AMIS2?
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Future Plans
• System test with strip modules of
 CERN buck converter PCB with discrete components (started)
 CERN AMIS1 with Bristol PCB inductors (asap)
 CERN AMIS2 buck converter ASIC (summer)
 CERN IHP buck converter ASIC (autumn)
• PCB development for integration of DC-DC converters into
tracker structures
• Automate and improve several existing test-stands (BCI, EMI, efficiency)
• Set up EMI-scanner to investigate coupling mechanisms of radiated noise
• Continue material budget studies
• Develop specifications for buck converter
• Get more practical experience with charge pumps
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Summary & Conclusions
• A bulk current injection test-bench for noise susceptibility studies
has been set-up and first measurements have been performed
• Various DC-DC converters have been tested in a 7T magnetic field
• Both set-ups need some improvements, but seem to be useful for
tests of future converter and module prototypes
• Simulation of material budget for powering/cooling schemes finished,
will be presented in the next meeting
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Back-up Slides
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The APV25
f = 1/(250nsec)
= 3.2MHz
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The APV25
1.25V
2.5V
*
* is connected to 2.5V since about 2000
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The APV25
1.25V
2.5V
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On-Chip Common Mode Subtraction
• 128 APV inverter stages powered from 2.5V via common resistor (historical reasons)
 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
pre-amplifier
V250
inverter
V250
R (external)
V125
strip
vIN+vCM
vCM
vOUT = -vIN
VSS
Node is common to
all 128 inverters in chip
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Common Mode & Differential Mode
Differential Mode (DM):
Source
Load
Source
Load
Common Mode (CM):
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AMIS1 Buck Converter w/ Ferrite Coil
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