Pixel Readout Electronics -Pixel Readout Electronics -from HEP to imaging to HEP…from HEP to imaging to HEP…

Status, requirements, new ideasStatus, requirements, new ideas

M. Campbell, R. Ballabriga, E. Heijne, X. Llopart, M. Campbell, R. Ballabriga, E. Heijne, X. Llopart,

L. Tlustos, W. Wong L. Tlustos, W. Wong

CERNCERN

Geneva, SwitzerlandGeneva, Switzerland

EUDET Annual Meeting 2007, ParisEUDET Annual Meeting 2007, Paris

OutlineOutline

BackgroundBackground TimepixTimepix

Description of circuit Demonstration with Si

Medipix3 Medipix3 Description of circuit First results

Medipix2 to Timepix to Medipix3 to … GasSiPix?Medipix2 to Timepix to Medipix3 to … GasSiPix? Requirements and possibilitiesRequirements and possibilities Summary and conclusionsSummary and conclusions

BackgroundBackground

Pixel readout developments at CERN started with LAA and Pixel readout developments at CERN started with LAA and then RD19 Collaboration – LHC R detector and Dthen RD19 Collaboration – LHC R detector and D

Work in RD19 was used directly by Omega, WA97 and NA57 Work in RD19 was used directly by Omega, WA97 and NA57 and indirectly by Delphiand indirectly by Delphi

Alice, Altas and CMS use pixel vertex detectors based on Alice, Altas and CMS use pixel vertex detectors based on hybrid pixels. (LHCb has a RICH detector using the hybrid hybrid pixels. (LHCb has a RICH detector using the hybrid pixels too) pixels too)

The Medipix1 imaging chip was a direct spin off of RD19 The Medipix1 imaging chip was a direct spin off of RD19 chipschips

The Medipix2 imaging chip was a separate development The Medipix2 imaging chip was a separate development using the same CMOS technology (0.25using the same CMOS technology (0.25m) as Alice, Altas m) as Alice, Altas and CMSand CMS

The Timepix chip (imaging and time tagging) comes directly The Timepix chip (imaging and time tagging) comes directly from Medipix2from Medipix2

Michael Campbell

From Medipix2 to TimepixFrom Medipix2 to Timepix

A novel approach for the readout of a TPC at the A novel approach for the readout of a TPC at the future linear collider is to use a CMOS pixel detector future linear collider is to use a CMOS pixel detector combined with some kind of gas gain gridcombined with some kind of gas gain grid

Using a Using a nakednaked photon counting chip Medipix2 photon counting chip Medipix2 coupled to GEMs or Micromegas demonstrated the coupled to GEMs or Micromegas demonstrated the feasibility of such approach feasibility of such approach

6 mm

2 mm

2mm

1 mm

e-

σpos

σcluster-size

14 mm

6 mm

2 mm

2mm

1 mm

e-

σpos

σcluster-size

14 mm

14.08mm

14.0

8mm

GEMMicromegas

50um

From Medipix2 to Timepix (contd)From Medipix2 to Timepix (contd)

These experiments These experiments ((by NIKHEF/Saclay, Freiburg 2004/2005 )by NIKHEF/Saclay, Freiburg 2004/2005 ) demonstrated that single electrons could be detected using a demonstrated that single electrons could be detected using a nakednaked Medipix2 chip Medipix2 chip 2D2D

Did not provide information on the arrival time of the electron in Did not provide information on the arrival time of the electron in the sensitive gas volume the sensitive gas volume 3D (position + time) !!!3D (position + time) !!!

To further exploit this approach the Medipix2 has been redesigned To further exploit this approach the Medipix2 has been redesigned to incorporate a time stamp with a tunable resolution of 100 to to incorporate a time stamp with a tunable resolution of 100 to 10ns.10ns.

Requirements:Requirements: Keep Timepix as similar as possible to Medipix2 in order to benefit from large

prior effort in R/O hardware and software Avoid major changes in pixel and/or readout logic – risk of chip failure due to

poor mixed mode modeling Eliminate 2nd threshold Add possibility of programming pixel by pixel arrival time or TOT information

This modification was supported by the JRA2/EUDET This modification was supported by the JRA2/EUDET Collaboration (www.eudet.org)Collaboration (www.eudet.org)

Timepix SchematicTimepix Schematic

Preamp

Disc

THR14 bitsShift

Register

Input

Ctest

Testbit

Test Input

Mask

4 bits thr Adj

Mux

Mux

Clk_Read

Previous Pixel

Next Pixel

Conf

8 bits configuration

Polarity

Analog Digital

Clk_Count

Timepix Synchronization

Logic

Clk_Countb

P0

P1

Shutter

Ovf Control

Clk_Read

Shutter_int

Michael Campbell

Timepix chip architectureTimepix chip architecture

IO

Logic

LVDS

In

LVDS

Out32-bit CMOS Output

256-bit Fast Shift Register35

84-b

it P

ixel

Col

umn

-035

84-b

it P

ixel

Col

umn

-0

Bandgap + 13 DACs

1612

0 m

14111 m

3584

-bit

Pix

el C

olum

n-1

3584

-bit

Pix

el C

olum

n-1

3584

-bit

Pix

el C

olum

n-2

5535

84-b

it P

ixel

Col

umn

-255

1408

0 m

(pix

el a

rray

)

Chip architecture almost identical to Chip architecture almost identical to Mpix2MXR20Mpix2MXR20

M0=M1=1 and Shutter ON -> FClock used as Ref_Clk

256x256 55µm square pixels256x256 55µm square pixels Analog Power -> 440mWAnalog Power -> 440mW Digital Power (Ref_Clk=50MHz) -> 220mWDigital Power (Ref_Clk=50MHz) -> 220mW Serial readout (@100MHz) -> 9.17 msSerial readout (@100MHz) -> 9.17 ms Parallel readout (@100MHz) -> 287 µs Parallel readout (@100MHz) -> 287 µs > 36M Transistors> 36M Transistors

Timepix Layout statusTimepix Layout status

11 22 44

55

66

33

55μm

55μm

Mpix2MXR20 layoutMpix2MXR20 layout Timepix layoutTimepix layout

11 22 44

55

66

55μm

55μm

DemonstrationDemonstration

6th June 2007.. Michael.Campbell@cern.ch

Limitations of TimepixLimitations of Timepix

Charge below threshold in shared events is Charge below threshold in shared events is lost in all modeslost in all modes

Charge measurement near to threshold in Charge measurement near to threshold in TOT is impreciseTOT is imprecise

Arrival time/TOT measurement range is Arrival time/TOT measurement range is limited by counter depthlimited by counter depth

Chip is neither triggerable nor data drivenChip is neither triggerable nor data driven There is no FAST-OR There is no FAST-OR

55

The winner takes all

• Charge processed is summed in every 4 pixel cluster on an event-by-event basis

• The incoming quantum is assigned as a single hit

Medipix3 – charge summing conceptMedipix3 – charge summing concept

gm

gm

Vfbk

PolarityBitGainMode

ThAdjustBitChSummingMode

Test Input

Input Pad

TestBit

B_TH<0:3>B_TH<4>

TH1

clustercommoncontrollogic

+Arbitration

circuitry

15 bits Shift

RegisterSR1

MUX

Previous Pixel SR1

Next Pixel SR1

ModeContRWDisablePixelCom

AdjustTHHModeCS_Cluster4

ANALOG DIGITAL

Cf

Ctest

To adjacent pixels (A, B, D)x3

From adjacent pixels (F, H, I)

x2

From adjacent pixels (A, B, D)

To adjacent pixels (F, H, I)

A B CD E FG H I

BLOCK DIAGRAM PIXEL E

Disc

DiscTH2

15 bits Shift

RegisterSR2

MUX

Previous Pixel SR2

Next Pixel SR2

x1

x3

Medipix3 – pixel block diagramMedipix3 – pixel block diagram

17 October 2006 Michael Campbell

2

1 3

4

5

6 7

DIGITAL CIRCUITRY

4. Control logic (124)

5. 2x15bit counters / shift registers (480)

6. Configuration latches (152)

7. Arbitration circuits (100)

Total digital 856

ANALOG CIRCUITRY

1. Preamplifier (24)

2. Shaper (134)

3. Discriminators and Threshold Adjustment Circuits (72)

Total analog 230

55

55

Front End Operating Front End Operating ModeMode

Single Pixel Single Pixel ModeMode

Charge Charge Summing ModeSumming Mode

CSA Gain (CCSA Gain (CFF)) 11.4mV/Ke- (C11.4mV/Ke- (CFF=14fF)=14fF)

CSA-Shaper Gain CSA-Shaper Gain 65nA/Ke- (High Gain Mode), 30nA/Ke- 65nA/Ke- (High Gain Mode), 30nA/Ke- (Low Gain Mode) (Low Gain Mode)

Non linearityNon linearity <5% 9Ke- (High Gain Mode) , <2% <5% 9Ke- (High Gain Mode) , <2% 22Ke- (Low Gain Mode)22Ke- (Low Gain Mode)

Peaking TimePeaking Time ~~100ns100ns

Return to baselineReturn to baseline <1<1s for 4Ke- (nominal conditions), s for 4Ke- (nominal conditions), <300ns (tuning R<300ns (tuning RFF))

Electronic noiseElectronic noise 72e72e-- r.m.s. r.m.s. 144e144e-- r.m.s. r.m.s.

Analog power Analog power dissipationdissipation

16.216.2W (nominal conditions)W (nominal conditions)

Medipix3 prototype – electrical measurements Medipix3 prototype – electrical measurements summarysummary

The Timepix chip, although funded by EUDet, evolved from the The Timepix chip, although funded by EUDet, evolved from the successful Medipix2 developmentsuccessful Medipix2 development

The ready availability of chips and readout systems led to the initial The ready availability of chips and readout systems led to the initial experiments with gas and Medipix2 and sped up enormously the experiments with gas and Medipix2 and sped up enormously the exploitation of Timepix by the users exploitation of Timepix by the users

The future Medipix3 chip is being developed to mitigate charge sharing The future Medipix3 chip is being developed to mitigate charge sharing in single photon counting. But like its predecessor Medipix2 it should in single photon counting. But like its predecessor Medipix2 it should provide building blocks, experience or even entire readout systems provide building blocks, experience or even entire readout systems which could be reused for a future single event processing chip which could be reused for a future single event processing chip

Given the length and cost of such developments it would make sense Given the length and cost of such developments it would make sense to cluster users around a single ASIC development (technology to cluster users around a single ASIC development (technology oriented development) …oriented development) …

Summary of present statusSummary of present status

Requirements for a general purpose Requirements for a general purpose gas and semiconductor readout chipgas and semiconductor readout chip

Clean hit informationClean hit information Low and uniform thresholdLow and uniform threshold High spatial resolutionHigh spatial resolution Combined energy and arrival time informationCombined energy and arrival time information

GasSiPix - Front endGasSiPix - Front end

Medipix3 or GOSSIPO-2 likeMedipix3 or GOSSIPO-2 like Suitable for semiconductors and gas readout? Rise time 25ns? Noise 100 e- rms? Minimum threshold 750e-? Power <1W/cm2?

For gas detectors include spark protection and SiProt shieldingFor gas detectors include spark protection and SiProt shielding Which A:Si thickness? How many pC should it withstand?

Use precision time tag unit from Nikhef (GOSSIPO-2 V. Gromov) in pixel to Use precision time tag unit from Nikhef (GOSSIPO-2 V. Gromov) in pixel to measure arrival timemeasure arrival time

1-2ns precision for Vernier counter? 15-bit clock tick counter?

Use TOT for energy measurement and/or timewalk correction if charge summing Use TOT for energy measurement and/or timewalk correction if charge summing not includenot include

8-bit TOT precision?

*** Basic idea developed together with Ruud Kluit of NIKHEF ***

GasSiPix - ReadoutGasSiPix - Readout

Triggered or data initiated?Triggered or data initiated? If triggered how/when is a pixel reset Fast OR in any case?

Hit pixels only?Hit pixels only? Region of interest?Region of interest? Fast serial or parallel bus?Fast serial or parallel bus? 4 side buttable?4 side buttable? What level of rad tolerance needed (given area penalty)? What level of rad tolerance needed (given area penalty)?

Summary and Conclusions Summary and Conclusions

Medipix2 spawned TimepixMedipix2 spawned Timepix The synergy between imaging and HEP is The synergy between imaging and HEP is

evident (to me)evident (to me) Medipix3 is in full developmentMedipix3 is in full development GasSiPix is technically feasible (within limits)GasSiPix is technically feasible (within limits)

Collaboration with people with differing Collaboration with people with differing requirements requires compromises on all requirements requires compromises on all sides but the outcome can be rewarding for sides but the outcome can be rewarding for all.all.

AcknowledgementsAcknowledgements

Fellow members of the Medipix2 and Medipix3 Consortia Fellow members of the Medipix2 and Medipix3 Consortia

See: www.cern.ch/medipixSee: www.cern.ch/medipix

Stanislav Pospisil and co-workers at CTU, PragueStanislav Pospisil and co-workers at CTU, Prague