07 October 2004

Hayet KEBBATI

-1-

Data Flow Reduction and Signal

Sparsification in MAPS

Hayet KEBBATI (GSI/IReS)

07 October 2004

Hayet KEBBATI

-2-

Pixel Sensors applied to vertex detector Hybrid Pixel Detectors

Fast readout and radiation hardness device,

Sizeable pixel pitch due to readout circuitry surface,

High material budget.

Charge Coupled Devices -CCD-

High density due to reduced pitch size,

Poor radiation hardness and long readout time.

Benefits from constant decrease of technology size higher pitch density,

Can be thinned down to the thickness wanted => less material budget compared to hybrid devices,

Fast readout and radiation tolerant compared to CCD,

But radiation hardness always far behind hybrid devices,

Cost-effective and easily available CMOS Process.

Monolitic Active Pixel Sensors -MAPS-

07 October 2004

Hayet KEBBATI

-3-

System on a Chip (SoC)Signal

Processing Part Sensor

Digital Part Digital Part Analog partAnalog part

Interface Part (ADC)

At the first Silicon tracking Station (5cm), particle densities have values up to 2 hits/mm².event,

Fast readout (100ns/event) Huge data flow 1.6 Tera bits/sec (output size=1 bit),

Hit Extraction and data sparsification Data flow of 8 Giga bits/sec

Implementation of on-chip processing forming a System on Chip

Parallel readout 40 transmission lines per reticle (20mmx20mm), Freq=200 MHz (output size=1 bits)

CMOS Sensor -MAPS- : Data Flow Reduction

07 October 2004

Hayet KEBBATI

-4-

• Control and address Electronics

• Fast signal processing and data sparsification Signal digitalisation

• Storage threshold values needed during data sparsification

• Surface ratio (B2/B1) must be as small as possible

Matrix of Pixel

Control ELN

Sparcification

Memori-sation

Smart Detector Reticle

Band Height of non-sensitive part B2

Sensitive part

Control and processing partADC

Band Height of sensitive part

B1

07 October 2004

Hayet KEBBATI

-5-

Charge Sensitive Element :CDS with clamping capacitor architecture

o nwell/p-epi diode biased by a bias forward diode to convert particle charge to voltage,

o Noise sources : shot noise, FPN, flicker noise and thermal => CDS technique

o On pixel CDS and amplification => good signal to noise ratio and T readout=100ns.

VA

Vclamp

vdd

gnd

gnd gnd

SFsample read

clam

pCac Cclamp

Csample

Vx

2 diodes’s Self reverse bias charge sensitive element

SFVout

07 October 2004

Hayet KEBBATI

-6-

Signal Sparsification Method

Hit2111001000100010

011001000112100

200100100010101

100100100010891

1001170000117111

000101100010351

001001000101000

111001000100110

101001230111101

2010029101110200

01010771120010

000010111101000

000010001100000

011001000100011

031001000101001

Clusters

Hit1

3 Steps : 1) Scanning clusters of 3x3 pixels

2) Compare pixels and clusters with seed threshold and cluster threshold value

3) Extract valid clusters

seed_thre=7 mv

cluster_thre=20 mv

07 October 2004

Hayet KEBBATI

-7-

Hit output = Wpix . 5 + Wadr (cluster 5)

Wpix Rocc Flow Reduction Ratio Data Flow/Reticle

3 bits 4% 67% 200 Giga bits/sec

8% 33%

10% 17%

4 bits 4% 70% 240 Giga bits/sec

8% 40%

10% 25%

Hit output = Wpix . 2 + Wadr (heavy center, processing part surface>>)

Wpix Rocc Flow Reduction Ratio Data Flow/Reticle

3 bits 4% 79% 128 Giga bits/sec

8% 57%

10% 47%

4 bits 4% 82% 144 Giga bits/sec

8% 64%

10% 55%

Data Flow with On-chip Processing

Rocc is the hit occupancy rate = number of hits / total number of pixelsWadr is the binary length of the address of the pixel positionWpix is the binary length of the signal corresponding to the pixel voltage

07 October 2004

Hayet KEBBATI

-8-

100 rows

1000 columns

1000 3bits ADC

Seed pixel and cluster Comparisons

Cluster Extraction

Threshold values Memorisation

Sub-bloc Detector Structure

Pitch = 20 µm

Pixel Readout time = 100ns => Readout time = 10 µs

=> occupancy rate up to 8% at station 1 closest to the beam Column parallel readout, Digitalization of the output data of each column (3 bits ADC).

(2 mm)

(20 mm)

Sensitive part

Control and processing part

07 October 2004

Hayet KEBBATI

-9-

8

OR Gates Tree

128

+++

+++

+++

+++

+++

+++

+++

+++

128

FSM

FIFO 8

ADC ADC ADC ADC ADC ADC ADC ADC

counter

OR Gates Tree

128

+++

+++

+++

+++

+++

+++

+++

+++

128

FSM

FIFO 8

ADC ADC ADC ADC ADC ADC ADC ADC

200 MHz

50 MHz

10 MHz

Surface = 20mm2

Processing surface to sensitive surface ratio=1/2

Data Sparsification Implementation results (0.35 µm)

07 October 2004

Hayet KEBBATI

-10-

row decoder

row decoder

row decoder

row decoder

column decoder

column mux, write buffers, sense amplifiers,

DRAM cell

writebit line

gnd

read

bit line

3 T DRAM 3.5 x 5.5 m = 2.5 x 3.92

SDRAM Memory Strucure

adr

write

datapre

read

adr

data valid data

Write CycleRead Cycle

07 October 2004

Hayet KEBBATI

-11-

• Memory of 512x26 bits in 0.25µm technology

• Regular layout with silicon surface saving

• Test data maintain time in DRAM cells

• Test of circuit behavior under radiation : number and type of errors

detection and correction bits

Surface : 320µmx930µmAccess delay : 2.5 nsPower dissipation: 7 mW

SDRAM Implementation Results

07 October 2004

Hayet KEBBATI

-12-

Summary Real-time data processingReal-time data processing

Readout time = 10µs => hit occupancy rate up to 8% in worst caseReadout time = 10µs => hit occupancy rate up to 8% in worst case

Processing surface to sensitive surface ratio = ½Processing surface to sensitive surface ratio = ½

To improve the ratio :To improve the ratio :

1.1. Increase the pitch Increase the pitch hit occupancy rate rise hit occupancy rate rise

2.2. Parallel readout by 2 rowsParallel readout by 2 rows High power dissipation High power dissipation

SDRAM design in 0.25 µm technologySDRAM design in 0.25 µm technology

Surface = 320µmx930µmSurface = 320µmx930µm

Access time = 2.5 nsAccess time = 2.5 ns

Options to reduce hit occupancy: Options to reduce hit occupancy:

Optimize STS geometry to avoid hot spotsOptimize STS geometry to avoid hot spots

? Use hybrid pixels in the hottest area? Use hybrid pixels in the hottest area