TTC = Timing Trigger Control
TTC system for
FP420 reference
timing?
Sophie Baron (PH-ESS)
Sophie BARON, PH-ESS
FP420 Collaboration meeting, Sept. 2006
1
FP420 requirements for timing transmission
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Bunch Clock and Orbit(?) to be transmitted
Level of radiations = ??
Clock monitoring between the 2 signals
10 ps rms jitter skew between the clocks in W and E
Sophie BARON, PH-ESS
FP420 Collaboration meeting, Sept. 2006
2
Existing system
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
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The TTC system
Rad-hard chips
Monitoring the phase between 2 optical signals
Various transmission schemes used by the TTC system
Typical jitter values
Sophie BARON, PH-ESS
FP420 Collaboration meeting, Sept. 2006
3
TTC system in one slide
Transmission of…
 Timing of the LHC from the RF source to the experiments
o LHC Bunch Clock (40.078xx MHz)
o Revolution Frequency (11.245x kHz)
Then combined inside the experiments with …
 Trigger and Control signals
 Used by front-end electronics and readout systems
…Using single optical fibres…
…and a lot of various components and modules…
Sophie BARON, PH-ESS
FP420 Collaboration meeting, Sept. 2006
4
Radiation hard components
 TTCrx:
o 50ps rms
o The TTCrx is now fabricated in the radiation-hard DMILL
technology, which completely eliminates the possibility of a singleevent latch-up, and should show a high immunity to single-event
upset (SEU).
o Tested up to : 8 Mrad (X-Rays) and – 5 x1013 n/cm2 (Neutrons)
 QPLL:
o 10-15ps rms
o Tested up to 10Mrad (Co-60 γ) + 3 1015 n/cm2
 TRR receiver:
o Optical receiver from Truelight (Taiwan) selected for most of the
TTC designs
o Tested with the TTCrx at the same doses.
o OK if the optical power level stays above -20dBm (0.1mW)
 Optical Fibers:
o sensitive to radiations (attenuation increases with the dose)
o Special fibres validated for ATLAS and CMS at high radiation levels
(1014-1015 n cm-2 and total dose of 100 to 300 kGy)
o
Sophie BARON, PH-ESS
Radiation hardness of multi-mode optical fibres for the ATLAS detector readout (June 1999,DG
Charlton et all)
FP420 Collaboration meeting, Sept. 2006
5
Clock differences Monitoring?
Comparator
control
 Phase shift with temperature:
o Typical value: shift of 25ps/degC/km
o FP420 => 12ps/C per side if 420m on each side
 Limit of the measurement:
o The jitter between the W and E zones can not be monitored, as it is
manly generated by the electronics doing the optical to electrical
conversion
o The measurement will only concern the phase shift between the 2
segments
Sophie BARON, PH-ESS
FP420 Collaboration meeting, Sept. 2006
6
Transmission Schemes
 Encoded
o TTC inside the experiments (based on aTTCrx chip)
o Advantage: Allows to encode the orbit signal (and control frames) to
the 40.078MHz
o Drawback: jitter increases with the quantities of encoded data
o QPLL added to reduce the jitter of the recovered clock down to 1015ps rms
 Parallel
o TTC backbone system
o Orbit and clock on separate fibres
o Advantage: very low jitter after the opto-electrical conversion (10ps)
without using the QPLL
Sophie BARON, PH-ESS
FP420 Collaboration meeting, Sept. 2006
7
Encoded Scheme [1]

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Used to transmit Timing, Trigger and
Control inside the experiments
B*
Serial transmission
A
2 Channels are transmitted
o A Channel:
40MHz Clock
• Broadcasting Orbit (or L1a in
TDM Encoder A B A B A B A B A B
experiments)
+ BPM
• Low latency
• Time critical signals
A
B*
o B Channel:
Orbit
(Idle)
• Framed & formatted commands
0
0
and data (Hamming)
0
1
• Broadcast or individually
0
1
addressed
1
1
• Internally used in the
experiments
A & B are Time Division Multiplexed
25ns
BiPhase Mark encoding is used at
160.316Mbaud: balanced signal
Sophie BARON, PH-ESS
FP420 Collaboration meeting, Sept. 2006
8
Encoded Scheme [2]
Encoder
& laser tx
Photodiode,
decoder &
clock recovery
Encoded Clock, A, B
TTCrq
CH. A (pulse, Orbit or trigger)
CH. B (serial data frame)
50ps rms cy2cy
Decoded CH. A
40MHz Clock
Recovered
Clock
TTCex
TRR
TTCrx
Clock
QPLL
Decoded CH. B
15ps rms cy2cy
Sophie BARON, PH-ESS
FP420 Collaboration meeting, Sept. 2006
9
Parallel Scheme
 Clock and orbit on parallel fibres
 RF signal transmission scheme
Picture
RF_Tx_D
Picture
RF_Rx_D
Tx Board
Rx Board
 Laser Types
o OCP03: 300 $
o OCP Tx 24: 600 $
Sophie BARON, PH-ESS
 Photodiode Types
o OCP Rx 03: 230 $
o OCP Rx 24: 300 $
o TRR: 8 CHF!
FP420 Collaboration meeting, Sept. 2006
10
Typical Jitter values – Parallel Scheme [1]
C1
OCP Tx 03
C3
C2
Comparator
control
TRR-1B43
+ fanout
+ECL driver
C1/C2
12.4ps
C1/C3
12.4ps
TRR-1B43
+ fanout
+ECL driver
C2/C3
6.5ps
Lecroy Wavepro 7100
1GHz
Sophie BARON, PH-ESS
FP420 Collaboration meeting, Sept. 2006
11
Typical Jitter values – Parallel Scheme [2]
C1
OCP Tx 03
C3
C2
Comparator
control
OCP Rx 03
+ fanout
+ECL driver
C1/C2
11.5ps
C1/C3
11.4ps
OCP Rx 03
+ fanout
+ECL driver
C2/C3
4.0ps
Lecroy Wavepro 7100
1GHz
Sophie BARON, PH-ESS
FP420 Collaboration meeting, Sept. 2006
12