Download ABCStar for ATLAS Strips

ABCStar for ATLAS Strips
(Front-End Electronics for the ATLAS ITk Strip Detector)
1-June-16
Francis Anghinolfi
CERN
For the ATLAS ITk Strips Community
Staves & Petals: Basic Integration Units
Each of 4 barrels will be
segmented into Staves.
Pictured here is the top side
of a double sided half-Stave.
Two half-Staves butt
together at Z=0, but
don’t connect
electrically.
module
bus tape
under sensor
strip
sensors
power
board
The End-cap disks will be
segmented into petals.
Pictured here is the hybrid
front side of a doublesided Petal.
FE-chip
hybrid
strip sensors
module
Hybrid control
chip (HCCStar)
Z=0 end
EndOfStructure card
(EoS)
FE-chip (ABCStar)
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power
board
EndOfStructure
card (EoS)
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A Very Large Increase in Size and Complexity
• Comparing the new ITk tracker to the existing ATLAS SCT:
• A factor of 4 more modules to build and a factor of 10 more channels to operate.
• Barrel Modules are built on sensors
Hybrid Control
Readout ASICs
9.8 cm x 9.8 cm in size.
ASIC (HCC)
(ABC)
• The inner two barrels have 4 rows of
2.4 cm long strips serviced by 2 readout
hybrids.
• The outer two barrels have 2 rows of
4.8 cm long strips serviced by one hybrid.
• End-cap modules use trapezoidal
shaped sensors of varying size to fit
the wedged shape petal.
Silicon
Sensor
• The longest End-cap strip is 5.4 cm long.
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Hybrid
LV/HV power
board
Barrel Module with Short Strips
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ABCStar – New Design
• After the first ABC ASICs (named ABC130) were
designed and fabricated on the IBM 130nm
technology, the ATLAS trigger rate requirement was
increased to 1 MHz.
• The ABC130/HCC readout architecture could not
support this 1 MHz rate and, therefore, a design
change was required.
• The fundamental change was the interface from
ABCs to the HCC as shown here.
• Serial transfer of data to the HCC was changed to
direct communication from all ABCs to the HCC –
hence the new ABCStar and HCCStar.
• The “star” configuration removed a bottleneck in
data transfer to the HCC, which had considerable
bandwidth still available.
• While both ASICs required changes, the HCCStar
requires nearly a complete redesign as it must now
essentially build events in parallel from fragments
coming from all the ABCStar.
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ABC130
ABCStar
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ABCStar - Standard Binary Readout
• The ABCStar front-end readout ASIC uses a similar binary readout as
employed by the present ATLAS SCT tracker readout.
• It includes amplifier, discriminator, pipeline for 256 channels, an event
buffer and a cluster algorithm to compress data for output.
• It is being designed to support more than one trigger mode:
• L0 – Capture & readout everything.
• L0/L1 – Capture data at L0, send
requested data at L1.
• L0/R3/L1– Capture data at L0, send
requested ROI data with priority,
send remaining requested data on
L1.
• The HCCStar manages these
three trigger modes and sends
the appropriate signals to the
ABCStar depending upon what mode is in
operation.
• ABCStar is built on the GF130nm technology.
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ABC130 Testing
> First 130 hybrid glued and wirebonded in F
mostly manually assembled)
• The ABCStar and HCCStar are still in design.
• The ABC130 & HCC130 are being used for testing and to
exercise module assembly and test.
• Even if the readout is different, the frontend part of ABCStar and ABC130
should be similar. Characteristics of the frontend are measured with the
ABC130.
Ingo Bloch | ITk
Single chip test board
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Hybrid (endcap)
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Module (barrel)
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ABC130 Testing
• Typical 1 channel data on module : Vt50, Linearity, Noise (threshold scan)
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ABC130 Testing
• One chip data (256 ch.) : Vt50, Linearity, Noise (empty, short strips)
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ABC130 Testing
• One hybrid data (2560 ch.) : Vt50, Linearity, Noise (empty, short strips)
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ABC130 Testing
• The noise on ABC130 was found to be higher (and gain lower) than expected
• Noise performance of the prototype front-end chip and the full
ABC130 front-end was compared.
• The prototype front-end allows comparison of performance of
negative & positive signals.
• ABC130 receives negative
signal only, whereas the
best performance in design
was for positive signal
ABC130 ENC on hybrid (ext cap.)
ABC130 ENC on prelim. module
Proto ENC for negative signal
Proto ENC for positive signal
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Response curves for positive and negative
polarities (same biases – no optimization, 2.5ns
calibration edge), measured on the prototype chip
Transfer Function
Transfer Function
600
Peak Height (mV)
Peak Height (mV)
400
400
200
200
0
2
4
Charge (fC)
6
Positive input charge:
- dynamic range <600mV
- Linear range ~450mV (~5fC)
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2
8
4
Charge (fC)
6
8
Negative input charge:
- dynamic range ~600mV
- Linear range ~400mV (~4fC)
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Gain for positive and negative signals (2.5ns CAL
edge) – Prototype chip
Gain as a function of channel
100
Normal Polarity
Inverted Polarity
Gain (mV/fC)
90
80
70
60
0
10
20
Channel Number
30
~20% effect!
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ENC for positive and negative signals (2.5ns CAL
edge) – Prototype chip
ENC as a function of channel
500
Normal Polarity
Inverted Polarity
Enc (e-)
450
400
350
0
10
20
Channel Number
30
~20% effect!
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Gain degradation for negative signal (n-on-p
detector)
Primary candidate: asymmetry caused by active feedback
(compression of the negative polarity signal caused by
modulation of the transconductance of the active feedback by the
signal)
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Architecture of the single channel
Input stage: active feedback (assymmetry for positive/negative input signals)
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Transient simulation – analog out
Discriminator input
2fC response
Input signal
POSITIVE
NEGATIVE
Only 6% effect on amplitude, effect not related to the amplitude of the input current
Slight degradation of amplitude for 5ns signal due to ballistic deficit
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Performance Difference with Signal Polarity
• Noise performance is worse after sensor polarity swap: effect of signal
compression.
NEGATIVE (faster, lower in amplitude, more noisy)
POSITIVE
• Effect of compression for negative signals (modulation of feedback
transistor gm) simulated at the 6% level, in reality (prototype
measurements) as high as 20%.
• This can be resolved by changing to a resistive feedback for ABCStar.
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Irradiation Testing
Changes for
the ABCStar front-end
• Feedback change to improve gain and
noise (+20% impact on power)
• Unexpected noise increase observed after ionizing
radiation:
• Possible reason: 1/f noise.
• Simulated pre-rad contribution of the
1/f noise to ENC was at the level of 3%.
• Radiation effects on 1/f noise under study.
• Some reports for similar technology (130nm ST)
show substantial increase of 1/f noise for regular
NMOS devices and no change for the enclosed
structures (influence of STI isolation?)
• For new ABC front-end, all critical (for noise)
NMOS devices will be in enclosed geometry.
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• ELT layout to reduce excess noise after
radiation
• Channel-to-channel mismatch
improvements
• Optimisation for the measured detector
parameters after full radiations
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Updated Backend for ABCStar
• The increase to 1 MHz event readout rate was the main concern for the change to
the “star” hybrid architecture.
• The L1 rate can be equal to L0 (flush all L0)
• The “regional” readout at reduced rate (~10% L0) is maintained. It is perceived as a
Priority Readout (L0_Priority) with low latency (to deliver for the L1track trigger)
ABC130
ABCSTAR
baseline
ABCSTAR
extended
ABCSTAR
All L0
L0 (event tagging)
400KHz
1MHz
1MHz
1MHz
R3 (L0-Priority)
10KHz
100KHz
100KHz
-
L1 (L0 read)
100KHz
400KHz
< 1MHz
1MHz
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FE
Hit Detect
Event Buffering in ABCStar
L0 Pipeline
12.8 μs
Event Buffer
128 slots
Cluster
Finder
Seriali
zer
L0
Event tagging
Fixed latency
Start
Low priority (L1)
read with tag,
free latency *
L1
Queue
Priority (R3)
read with tag,
free latency **
R3
Queue
Priority
* : up to the maximum possible number of events stored in the event buffer
** : limited by the L1-track construction (5us)
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Managing the 1 MHz L0 Rate
• The change to the “star” hybrid architecture was not the only concern with the
increase to 1 MHz event readout rate:
• The latency requirement for L0-P trigger is below 5us, to feed data to L1-Track
• Here are simulations of the readout time at two different output bandwidths.
The simulated latency for all data from 99% of all requests to arrive at the end of stave/petal
for the highest occupancy Barrel and End-Cap layer module of the ITK as a function of the L0
rate for the scenario where all L0 events are read out from the detector. Detector occupancies
commensurate with a mean occupancy of 200 separate pileup interactions per bunch crossing
have been used.
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Data formats and rates
One 160Mb/s output signal to the HCCStar
Physics data contains “cluster packet” of 12 bits (Channel ID + 3 adj. strips)
Full packet made of 4 bits Header, 16 bits for event ID, then 4 cluster packets max.
If more than 4 clusters a second Full packet is generated
68 bits
The estimated average event size per chip is 2 to 3 clusters (therefore one 56 bits packet)
The average data rate at the output of one ABCStar chip is 56 Mb/s
160Mb/s readout rate was rather chosen to reduce the transmission latency for L1-track
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L0-Tag
• ITk **may** employ a scheme to identify L0.
• Each L0 trigger will be accompanied by a tag; that tag will be sent back as part of
the event data; off-detector electronics will check for matching tags.
• The off-detector electronics then will have responsibility to manage the counter
identifiers.
ves
yy
ide
Group of 4BC
7 bits L0-Tag
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L0 distribution in 4BC
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Summary
ABCStar is currently under development with the following targets :
• Front-end :
• Adaptation to the detector signal polarity and to the detector
parameters after irradiations
• Removal of Excess noise after a few Mrads
• Back-end :
• Low latency Readout for L1_track
• 1MHz full readout
• Various readout scenarios “still” under considerations
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Backup
BACKUP
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A.A. Grillo 25
Preamplifier output
NEGATIVE
POSITIVE
Preamp response: only 1% effect on amplitude but different timing: negative
pulse faster and shorter what can explain difference of 6% after the shaper
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Shaper output
NEGATIVE
POSITIVE
Shaper response: 6% effect on amplitude and different timing: negative pulse
faster and shorter
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Post Irradiation Testing
At low temperature/low dose rate
(2krads/hour)
• Digital current rise with TID observed in
ABC130.
• Known effect: see e.g. F. Faccio and G.
Cervelli, IEEE Trans. 52.6 (2005) 2413.
• Digital current (D) peaks, then recovers.
Function of dose rate and temperature. No
effect in analogue current (A). ABC tested
configured & unconfigured.
• Tests underway at expected operating
temperature and dose rate at HL-LHC.
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A.A. Grillo 28
UVM functional verification setup
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HCC* Block Diagram
From ABC
• The HCC* provides all I/O control for
itself and the multi-ABC* readout
system.
• Trigger types and commands for
configuration, calibration, etc. are
received and passed onto ABC*s as
needed.
• Data from all ABC*s is grouped by
event and then sent out.
• It is also built on the GF130 nm
technology.
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Module is the Basic Building Block
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Front-end
Digital
6.8mm
• This diagram depicts a short strip barrel module
with a blow-up of an ABC130 front-end ASIC.
• Each of the two readout hybrids contains 10 ABCs
and one HCC module controller ASIC.
• Sitting between the two readout hybrids is a
power board.
• A long strip barrel module would have one hybrid
and one power board.
• The power board includes a DC/DC converter to
supply 1.5V, an HV switch for sensor bias and an
AMAC (Autonomous Monitor & Control) ASIC.
• AMAC is powered independent of the DC/DC
converter, monitors temperature, voltage, etc. and
controls an HV switch and power to hybrid(s).
• Bidirectional communication with AMAC is
provided via I2C bus from the SCA block of the
LpGBT at end of stave or petal.
• LV to the hybrid and HV to the sensor can be
controlled based upon correct temperature and
operating voltages and currents.
• The End-cap modules differ in the size and shape of
the sensor and in the number of ABC ASICs.
7.9mm
SLVS I/O
Power input
SLVS I/O
Power Board: DC/DC, HV Mux, AMAC
Sensor
Short Strip Barrel Module
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Stave or Petal Connections
One of Two Sides
LpGBT
(1 or 2)
e-Links
ABC*
...
H
C
C
ABC*
*
Readout Hybrid
1 or 2 Hybrids
per sensor module
Power Supplies
US(A)15
~48V?/~15V?
A
M
D
A
C HVsw
C
⁄
Power Board
D
C
Cu-Kapton
Bus Tape
I2C
Up to 14 Modules on Bus Tape
PP3
DC/DC?
~48V->12V?
D
C
⁄
D
C
EOS
VL+
Service
Module
PP2
Voltage
Clamp?
PP1
HV Supplies
US(A)15
• Here are all the connections
for readout, control & power.
• I will focus on each part one by
one.
Optical
Fibres
ITk Data Handler
Monitor/Calibration
DCS
TTC
High Speed Network
ATLAS DAQ
FELIX
L1 Track
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End of Structure (EOS card) & PP1
• Each side of a petal and each side of a halfstave has an EOS card.
• Petals with 14 HCC*s (Some modules have 2
hybrids and 2 HCC*s.) and outer barrel halfstaves with 14 HCC*s require 1 LpGBT – Inner
barrel half-staves with 28 HCC*s require 2
LpGBTs, each with a complementary number
of VL+s.
• A DC/DC converter steps down the voltage
for the EOS ASICs.
• PP1 provides the connection point for
harnesses from the outside and the Service
Module will provide an
orderly method to tie the PP1 connections to
the EOS cards.
LpGBT
(1 or 2)
D
C
⁄
D
C
EOS
VL+
Service
Module
PP1
Optical
Fibres
Concept of PP1 with
Service Module behind
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