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Experience with the Beetle1'2

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Experience with the Beetle1.2. 80MHz Digital Switching Noise ... Stems from digital circuit and multiplexer (tested by cut in power line internal to the Beetle) ... – PowerPoint PPT presentation

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Title: Experience with the Beetle1'2


1
Experience with the Beetle1.2
  • 80MHz Digital Switching Noise on the analog lines
  • Common Mode Problem
  • How to kill a Beetle chip
  • Conclusions

Stephan Eisenhardt University of Edinburgh
LHCb week, Electronics, 19.05.2003
2
80 MHz digital switching noise
  • As discussed at VELO Beetle meeting 30.04.2003
  • 80 MHz noise on analogue outputs and DataValid
  • Stems from digital circuit and multiplexer
  • (tested by cut in power line internal to the
    Beetle)
  • Different claims whether pos. or neg. parts of
    LVDS signals have larger contribution
  • No understanding at that time
  • Meanwhile understood, fix for Beetle1.3 proposed
    (Nigel)

data frame (128 ?4)
data frame (128 ?1)
DataValid
1-port data out
4-port data out
3
Edinburgh Setup
  • Beetle1.2 data frames pedestal
  • MaPMT test pulses
  • Edinburgh setup

Single pedestal event
Beetle1.2
solder bridges
128 ? 1 data frame
12-channel read-out
Testpulse mode
single base
LED direct or via optical fiber
8 dynode MaPMT
4
Common Mode Problem I
  • We use direct coupling for the signals (not
    capacitive decoupling)
  • We need as CM of lt2Noise for the binary readout
    of the MaPMT
  • We find
  • For bare HD board direct coupling CM of 50 of
    header bits
  • For bare HD board capacitive coupling CM not
    visible on scope

HD board without front-end
5
Common Mode Problem II
  • By attaching the front-end we find
  • CM increases by factor 4
  • (that fills the dynamic range of our ADC)
  • Main components inducing CM
  • tracks on HD board
  • cable connection to base
  • MaPMT itself
  • Shielding of cables reduces CM to lt50 of maximum
  • (limit of possible reduction not yet clear, but
    it looks very hard to get it down to our needs)
  • No trigger phase or other parameter dependence
    found
  • Looks like a ringing and/or RF problem, probably
    induced by inductance in GND line
  • Board Beetle is designed with low inductivity in
    the front-end
  • But we still may be forced to go for and analog
    readout option!!!

with front-end and MaPMT
6
How to kill a Beetle chip
  • _at_ Heidelberg
  • supply voltages gt2.7V with 50? serial resistors
    at the output
  • Understood as too high current density in the
    output (multiplexer?)
  • Can be prevented by higher serial resistor
    (proposed 300?)
  • Seems not very worrying as there is a hardware
    fix (off-chip)
  • _at_ Edinburgh (MaPMT)
  • short circuit between supply voltage 2.5V and
    GND on HD mother board
  • First (still with 50? serial termination)
    software reset feature broken, i.e. fault in the
    control logic but rest of chip still working
  • Second (now with 130 ? serial termination we
    need that to cover the 01.5V range of our ADC)
    fault in the pipeline, i.e. no output at all
  • Due to voltage spikes?
  • Related to overvoltage problem?
  • Worrying, as in the final detector a voltage
    glitch could kill many of your chips
  • _at_ CERN (VELO)
  • sudden death over night due to unknown reason
  • Very worrying, what is going on there? (again
    voltage spike?)
  • This is not yet understood

7
Conclusions
  • The Beetle still is fun to work with !!
  • Second hand information tells that the 80MHz
    noise will be under control in Beetle1.3
  • The source of common mode is not yet finally
    understood
  • The level of common mode with the direct input
    option may prove to be a killer for the binary
    readout option of the MaPMT,
  • i.e. we would have to go for the more expensive
    analog readout option
  • The causes of chip kills have to be understood
    and fixed,
  • as a full scale system cannot live with the
    thread of a large number of chips damaged by e.g.
    a power surge

8
Spare slides
9
3-bit comparator in Beetle1.2
  • from discussions with Hans Verkoojien
  • 1 MIP 22000e- 1538mV
  • comparator DC offsets ? 26mV (3?)
  • trade off
  • range covered at a time vs. resolution,
  • e.g. 140mV, 220.0mV, 410.0mV or 85.0mV
  • Comparator buffer gain 0.7
  • Beetle1.2MA0 12-dyn 300000e- ? 30mV
  • Signal 300000e- ? 0.730mV 21mV
  • Noise 7500e- ? 0.70.75mV 0.525mV
  • Beetle1.2 8-dyn 50000e- ? 85mV
  • Signal 50000e- ? 0.785mV 60mV
  • Noise 1000e- ? 0.71.7mV 1.2mV

Idelta Vdelta Vdelta range Vdelta step
size 0.125?A ? 2.5mV 04.375mV ? 0.625mV
? 0.250?A ? 5.0mV 08.75mV ? 1.25mV
? 0.625?A ? 12.5mV 021.875mV ? 3.125mV
? 1.250?A ? 25.0mV 043.75mV ? 6.25mV ?
No access to negative DC offsets!!
10
5-bit comparator in Beetle1.3 (08/2003)
  • from discussions with Hans Verkoojien
  • 1 MIP 22000e- 1538mV
  • comparator DC offsets ? 15mV (3?)
  • wrt. Beetle1.2
  • comparator input buffer gain 0.7 ? 1.0
  • DC offsets reduced due to removal of one buffer
  • Beetle1.3MA0 12-dyn 300000e- ? 30mV
  • Signal 300000e- ? 1.030mV 30mV
  • Noise 7500e- ? 1.00.75mV 0.75mV
  • Beetle1.3 8-dyn 50000e- ? 85mV
  • Signal 50000e- ? 1.085mV 85mV
  • Noise 1000e- ? 1.01.7mV 1.7mV

Idelta
Imain
Idelta- Imain
Idelta Vdelta Vdelta range Vdelta step
size 0.125?A ? 2.5mV 04.84375mV 0.15625mV 0.625
?A ? 12.5mV 024.21875mV ? 0.78125mV ? 1.000?A ?
20.0mV 038.75mV ? 1.25mV ?
Access to negative DC offsets possible!
11
Beetle1.2 Heidelberg board I
board at Oxford
  • at Edinburgh
  • Heidelberg mother- and daughter board
  • Beetle1.2 mounted on daughter board
  • Beetle1.2MA0 as soon as available
  • connect 8/12-stage MaPMT to this read-out

daughterboard with Beetle1.1
motherboard
  • What can be done with it
  • readout up to 12 MaPMT channels of 8 dynode stage
    MaPMT
  • analog and binary readout
  • 128 ? 1 and 128 ? 4 multiplexing (in 3600/900ns
    per event)
  • existing FED/MIDAS/VME DAQ can read this out
  • proof of principle for Beetle1.2 / 8-dynode MaPMT
    combination
  • proof of principle for Beetle1.2MA0 / 12-dynode
    MaPMT combination

12
How to readout a full MaPMT?
design PCB board Beetle
  • allows readout for 1 Beetle1.2(MA0) and 2(1)
    MaPMTs per board
  • no Kapton cables, flexible for 3x3 and 4x4
    geometry in the test beam
  • not yet settled symmetric GND lines? (PGA 10x8
    instead of 9x8)
  • time scale for production 1 engineer x 2 months
  • main tasks lay out signal traces pitch adaptor
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