LHC POWER CONVERTER
Radiation analysis
13/09/2011
TRAD, Tests & Radiations
Introduction
 The aim : to use TRAD experience in spatial
applications and to apply existing literature to
propose test recommendation for radiation
characterization compliant with LHC environment
 search of radiation tests data on the different types
performed on public data base
 references chosen by CERN designers : radiation data
analysis & complementary radiation tests needed.
 Then we propose radiation characterization
recommendations and priority for the different component
families : High, medium, low.
 Irradiation facilities.
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LHC RADIATION ENVIRONMENT
 Maximum radiation level for 10 years LHC
operation
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Total Ionizing Dose
 100 Gy for 10 years : level rather low but some devices
are excpected to show degradation
 ELDRS has to be taken into account
 Based on specifications for spatial application Margin
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TID Statistical approach
 Delta XL = <delta x> +/- K(n,C,P) σ
 There is a probability P with a confidence limit C that a given
electrical parameter will not exceed the following limits Delta XL
 <delta x > is the mean shift among tested population of n
samples, σ is the standard deviation of the shift, K is the one
sided tolerance limit factor.
 A 3-sigma (K=3) approach is often used in spatial
applications, with n=5 (samples) it will yield a
probability of success P>0.9 with a confidence level
C>0.9
 90% of parts from a given lot have a failure level above the type
TIDS, with a confidence level of 90%.
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Displacement Damage
 Tunnel : 3 e11 1MeV neutron/cm² for 10 years
 Devices concerned : Optocouplers, bipolar
transistors, operational amplifiers, comparators,
voltage reference,…
 shielded area : 6 e10 1MeV neutron/cm2
 only a few high precision components may show a
significant degradation.
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Single Event Effects: Thermal neutrons

10B loacted near the sensitive nodes of the devices.




The two recoils (Li and He) ions
BPSG in CMOS devices for technology nodes of 0.15µm and older.
P+ zones doped with boron give sensitivity to thermal neutrons.
So thermal neutrons effects need to be evaluated on digital devices
(FPGA, SRAM,..)

in priority : technology node >150nm.



The observed SEU sensitivity ratio is about two decades (typically 5E-14 cm2/bit with BPSG and 5E16 cm2/bit without BPSG).
Thermal neutron effects have been studied mostly on digital devices.
analog devices considered to be immune, to be checked for devices very
sensitive to SET with High Energy neutrons
facilities,



ILL in Grenoble
LLB in CEA/Saclay
other reactors with a moderator to enhance the thermal/high energy ratio
can also be used.
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Single Event Effects: High Energy Hardrons
 The variation of sensitivity of the different devices to
the energy of the incident hadrons is complex.
 the cross-section is considered in a first
approximation as constant for energy>20MeV
 But for some particular effects such as SEL, SEB,
MCU and ASET (Analog Single Event Transients) this
assumption is probably not sufficient.
 Both LET and range (related to energy) of the
secondary recoils are important parameters to
induce these SEEs.
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Heavy Ions testing approach
 Heavy ions testing is proposed to obtain the
LET threshold to trigger SEL.
 If LETth<15 MeV*cm2/g there is a high
probability that SEL will be observed with
HEH.
 This approach will not give the SEL crosssection for the LHC environment but will
indicate if SEL tests are needed in an
environment representative of the LHC
environment.
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OP27 : bipolar technology, high precision
operational amplifier

Radiation data :

Testing recommendation


OP27 operational amplifier can be used for LHC tunnel
environment.
A proton test (both TID and DD) should be performed to
evaluate the degradation of the most sensitive parameter
Ibias.
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TRAD, Tests & Radiations
LM139 : precision voltage comparators
 Radiation data :
 Total dose: Input bias current drift @ 20krad
 SET: cross-section and Threshold LET related to
the voltage difference between inputs.

dV=12mV: sigma=4E-9 cm2
 Testing recommendation
 A proton test (TID-DD) is needed to evaluate input
current, gain, output current.
 A high energy proton test to evaluate SET in worst
case condition (Input voltage difference=10mV)
should be performed
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UC1842
 Radiation data
 No SEL @ LETth >85 MeV.cm2/mg (Warren)
 TID:
 Vref: 15 krad
 Other parameters >50krad
 ASET
 Protons: Cross-section 5E-10 cm2
 Testing recommendation
 UC1842 can probably be used in the application: Verify the
effect of a variation of Vref, on the output voltages in the
application.
 TID: Vref @ H4Irrad.
 ASET: protons
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LTC1595 16 bits DAC
 Radiation data
 SEL LET threshold of about 10 MeV-cm2/mg
 cross section relatively small at low LETs, gradually increasing to
about 10e-4 at high LET
 factor of 1.5 to 2 increase in latchup cross section for the heated
device.
 Testing recommendation
 SEL: static test
 Electrical conditions: Vdd= Vddmax Vref=Vref nom.
 Effects of input state on SEL sensitivity: LD, CLK, SRI will be put at 0 and then at 1.
 Out1 at Gnd,
 Total dose:
 Bias under irradiation: Vdd nom, Vref nom :External high stable power supply , CLK (at
a given frequency), 0 is stored in the register (Power On Reset),
 Control: Power supply current, Output current (OUT1)
 Detail test at several steps.
 SET test




Room temperature test
Codes input: all0 or all1
Observation of output with an Operational Amplifier.
Measurement of SET amplitude and duration related to switches and register bits upset.
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TRAD, Tests & Radiations
AD768 AD 16 bits DAC
 Radiation data
 TID : tested biased at high dose rate within specifications up to 50
krads.
 SEU LETth of about 15 MeV-cm2/mg
 All of these SEU occur in the standby mode.
 A simple reclocking of the data reset the device.
 The device was tested at constant oscillation frequencies of 0.5, 1, and 12 MHz. No
SEUs were seen at these frequencies.
 The device is apparently immune to SEU effects at frequencies over 0.5 MHz.
 Testing recommendation
 SEL test
 The SEU rate is related to the refreshing frequency of the device.
At high frequency (>0.5 MHz) the probability of upset can be
neglected
 TID and DD: The technology of AD768 is ABCMOS1 from Analog
Devices. So ELDRS effects can exist.
 Test to be performed at H4IRRAD in active mode.
 Bias: nominal on VDD and VEE.
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AD7846SQ AD

Radiation data
 TID



DNL exceeds specification limit at 10krads(Si).
Functional failure at 15krads(Si), recovered after 168 hour annealing., parametric degradation
continues.
Devices were taken to 20krads(Si) and no functional failure was observed. After 25krads(Si), functional
failures were again observed.
 SEL threshold > 110

Testing recommendation
 SEL test is not mandatory because SEL was not observed with heavy ions
at maximum LET.
 SET: The output is a voltage output (A3 is the inside output amplifier).
Output transients and outputs voltage variation will be monitored during
irradiation.
 Total Dose and DD




Test performed at H4IRRAD
Use of an external low noise high stability voltage reference
Parameters monitored: output voltage, power supplies Vcc, VDD, Vss current
Detailed linearity test before and after irradiation.
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LTC1609 16 bits ADC
 Radiation data
 14 MeV neutrons
 No SEL events were detected after a fluence of 2e10 neutrons per cm2. The
limiting cross section 1.9 e-10 cm2
 HI
 At room temperature, SEL LETth between 8.0 and 11.7 MeV-cm2/mg.
 For the heated device, SEL LETth between 5.3 and 8.0 MeV-cm2/mg.
 Testing recommendation
 SEL to be performed at high temperature at maximum
values of Vdig and Vana.
 Total dose and DD:
 Tests to be performed at H4IRRAD to study simultaneously DD and Total
dose.
 SET and SEU
 Output binary code modifications to analyze for a stable input condition.
 First the stability of the code values to evaluate without radiation in the
facility. A window of coding is defined that take into account of all sources of
noise (Example + or -2bits around the code value). Only codes outside this
window are considered as SET.
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Tests recommendations and priorities
 Discrete devices
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TRAD, Tests & Radiations
 Linear devices
 Mixed devices
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 Digital devices
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TRAD, Tests & Radiations
SEE Irradiation facilites
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TRAD, Tests & Radiations
SEE Irradiation facilites
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TRAD, Tests & Radiations
SEE Irradiation facilites
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TRAD, Tests & Radiations
Conclusion
 radiation characterization recommendations can be
used as a guideline for the test campaign phase.
 The radiation effects on the different families have
been identified in WP2 and the radiation test
priorities are evaluated with three criteria: high,
medium, low.
 All the testing recommendations, derating rules are
given as a guideline and have to be used with
precaution.
 In some particular cases (application, very sensitive
parts…) this recommendation could be not
applicable and radiation testing remains the only
way to characterize the part sensitivity.
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