The CBC2 ASIC for

2S Modules at HL-LHC

Davide Braga

IOP 2014 Joint HEPP and APP Groups Annual Meeting, Royal Holloway, May 2014

Outline

•Tracker upgrade & detector module

•The CMS Binary Chip (CBC) v.1 & 2

•CBC2: architecture & performance

•CBC2 testing

• Beam test

• TID test

IOP 2014 MeetingDavide Braga, IC 2

Davide Braga, IC IOP 2014 Meeting 3

Phase-II upgrade of the CMS Strip Tracker

• Baseline design: Barrel+5Endcaps

• Based on 2 module types only

• Provides at the same time:• readout data upon receipt of L1 trigger• trigger data @40MHz (10 trigger hits up to η=2.5)

2S strip-strip double-layers~8400 modules~34M channels~155m2

PS strip-strixel double-layers~7000 modules~230M channels~62m2

IOP 2014 Meeting 4

Basic trigger module concept

Pass Stub Fail

R

f

~200μm

~100μm

~2-4 mm

outer sensor

inner sensor

• High-PT tracks (stubs) can be identified if cluster centre in top layer lies within a

search window in R-Φ (rows)

• pT cut given by: module radius (z), sensor separation and correlation windowDavide Braga, IC

IOP 2014 Meeting 5Davide Braga, IC

4 mm

5 mm

7 m

m

11 m

m

CBC1

CBC2

2 versions have now been produced - both in 130nm CMOS

CBC1 (2011)• 128 wire-bond pads, 50 mm pitch• front end designed for short strips, up to 5 cm

DC coupled, up to 1mA leakage tolerant, both sensor polarities

• binary unsparsified readout• pipeline length 6.4 msec

• chip worked well in lab and test beam• no triggering features

CBC2 (January, 2013) • 254 channels• ~same front end, pipeline, readout approach as CBC1 • bump-bond layout• includes triggering features

CMS Binary Chip (CBC)

IOP 2014 Meeting

rf

beam

offset windowwidth

top layer clusters

bottom layer clusters

zerooffset

Cluster width discrimination (CWD) logic

exclude clusters with hits in >3 neighbouring channelswide clusters not consistent with high pT track

Offset correction & correlation logic

for a cluster in bottom layer, look for correlating cluster occurring in window in top layer

window width controls pT cutstub found if cluster in bottom layer corresponds to cluster within window in top layer

window width programmable up to ± 8 channels

offset defines lateral displacement of window across chipprogrammable up to ± 3 channels

n

n+1

n-1

1/2/3 stripcluster onchannel n

programme clusterwidth to accept

channelcomparator

outputs

CWD logic

Stub finding logic

6Davide Braga, IC

IOP 2014 Meeting 7

CBC2 architecture

pipe. control

FE amp comp. pipeline shift reg.

vth

vth

vth

vth

256 deeppipeline

+32 deepbuffer

testpulse

biasgen.

fastcontrol

slow control

stu

b sh

ift r

egis

ter

offs

et c

orre

ctio

n &

cor

rela

tion

clus

ter

wid

th

disc

rimin

atio

n1

254 40 MHz diff.clock

signals in blue are single-ended

trig’d data out

stub shift reg. O/P

trigger O/P

I2C

254 channels: 127 from each sensor layerchannel mask: block noisy channels from trigger logicCWD logic: exclude wide clusters >3correlation logic: for each cluster in lower layer look for cluster in upper layer windowtrigger output: 1 bit per BX indicates correlation logic found one (or more) stubs triggered data out: unsparsified binary data frame in response to L1 trigger

nearest neighbour signals

T1 triggerfast resettest pulseI2C refresh

4 4 11 11

chan

.

ma

sk

4 4 11 11

nearest neighbour signals

reset

OR_254

OR_stubs

Ck

Davide Braga, IC

IOP 2014 Meeting 8

CBC2 performance

• All core functionality meets requirements

• Correlation functionality verified with test pulses,cosmics (backup), and in test beam

• Analogue performance close to simulation and specifications

e.g. 1000e noise for 5 cm strips (~8 pF)achievable for total channel power of 350 uW

noise & power vs. external capacitance

no

ise

[eR

MS]

po

we

r/chan

. [uW

]

external capacitance [pF]

electronsmode

/ measured/ simulation

1200

1000

800

600

400

200

0121086420

400

350

300

250

200

150

100

100

80

60

40

20

0

num

ber

of e

vent

s

600500400300200

comparator threshold VCTH [mV]

1 fC

8 fC

S-cu

rves

channel offsets tuning

coun

ts

comparator threshold [I2C units]

holesmode

before tuneafter

100

80

60

40

20

0200180160140

M. Raymond

Davide Braga, IC

CBC2 testing activities

Wire-bond CBC2• Useful to develop wafer probe procedures

• X-rays TID testing

2xCBC2 hybrid• Hybrid characterization and chip integration

• Bump-bonded ASICs

• Inter-chip links & logic

Davide Braga, IC IOP 2014 Meeting 9

2xCBC2 mini-module + sensor• Sr-90 source

• Cosmic rays

• Beam Test

IOP 2014 Meeting 10

Pt module beam test at DESY

TOP VIEW: strip direction into page

positron beamlow angular divergence (small angular error)

scintillator scintillator

module #4 on rotation stage

module #3 on fixed assembly

Mimosa26 MAPS (DATURA telescope)

~3 GeV e+

Daturatelescope

planes

pTmodule

• December 2013

• 4 GeV positron beam

• Datura telescope + 2 pT modules (1 rotatable to

simulate B-field effect) + 2 different strip sensors

• Custom control and DAQ

Davide Braga, IC

S. Viret

Davide Braga, IC IOP 2014 Meeting 11

Beam test results

Pt Selection cut: simulation measured efficiency

Other measurements include:

• Study of cluster width

• System noise

• Beam profile

avg. cluster widthvs

angle of incidence

EXP. pT cut: 2.14 GeV/cFIT: pT cut: 2.17 GeV/c σ: 0.1 GeV/c

M.Pesaresi

reconstructed pT cut of r=75cm layer

Incident Angle

Clus

ter W

idth

Total Ionizing Dose test

• First xray irradiation to 10 Mrads

• CBC2 operated continuously during irradiation

• monitored currents, biases, pedestal, noise

• no significant change in performance, moderate

increase in current before annealing

• Next: TID test up to ~50 Mrads

Davide Braga, IC IOP 2014 Meeting 12

Xray tubeCBC2

Bias/readout

IOP 2014 Meeting 13Davide Braga, IC

Milestones so far: CBC2 working to specs

Stub finding logic functioning TID dose irradiation test under way

First prototype version of 2S module extensively tested Beam test at DESY successful Pt selection cut and stub logic demonstrated DAQ working well

Future work:• Continue with 2S module prototyping

(8chip hybrid from CERN)• SEU test of CBC2• CBC3: final prototype version with full stub readout

First results to prove the track-trigger concepta very new idea never before implemented

CMS ambitious plans for a track trigger look promising

Conclusions and Future Work

A. Honma