Channel control ASIC for the CMS hadron calorimeter front end readout module Page: 1 of 4
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FERMILAB-Conf-02/210 September 2002
Channel Control ASIC for the
CMS Hadron Calorimeter Front End Readout Module
R. J. Yarema, A. Baumbaugh, A. Boubekeur, J. E. Elias, and T. Shaw
Fermilab, P. O. Box 500, Batavia, Il, USA
firstname.lastname@example.org, email@example.com, firstname.lastname@example.org, email@example.com, firstname.lastname@example.org
The Channel Control ASIC (CCA) is used along with a
custom Charge Integrator and Encoder (QIE) ASIC to digitize
signals from the hybrid photo diodes (HPDs) and
photomultiplier tubes (PMTs) in the CMS hadron calorimeter.
The CCA sits between the QIE and the data acquisition
system. All digital signals to and from the QIE pass through
the CCA chip. One CCA chip interfaces with two QIE
channels. The CCA provides individually delayed clocks to
each of the QIE chips in addition to various control signals
. The QIE sends digitized PMT or HPD signals and time
slice information to the CCA, which sends the data to the data
acquisition system through an optical link.
The CCAs and QIEs are mounted on the Hadron
Calorimeter Front End Module as shown in Figure 1.
Figure 1: Front End Module block diagram
Each CCA has two channels for control of two QIEs. For
efficient use of the optical fibres, three CCAs feed data to two
gigabit optical links, (GOLs) that drive vertical cavity surface
emitting lasers (VCSELs). Figure 2 shows the front side of
the Front End Module. The VCSELs are mounted on the
back of the board.
The CMS QIE is a full custom BiCMOS ASIC designed
by Tom Zimmerman and Jim Hoff at Fermilab. The QIE has
an embedded non-linear FADC that digitizes signals over a
wide dynamic range. The QIE operates in a 4-step pipeline
mode. Data is output as a 2-bit exponent and a 5-bit mantissa
along with the time slice information, which is referred to
Work supported by the Department of Energy under contract
as CapID, as shown in Figure 3. Choice of the PMT or the
HPD input is made by connecting power to either the PMT or
the HPD input amplifier in the QIE.
Figure 2: Front End Module circuit board
HPD Input 2 Exponent
Q 5 Mantissa
PMT Input 2 Cap ID
Figure 3: QIE signals
II. OPERATION OF CCA
The CCA is a multi-function device whose design is
intimately tied to the requirements of the QIEs. The CCA has
two major functions:
" Send individually programmable delayed clocks to each
of the QIEs, to correct for time differences within the
hadron calorimeter (58 nsecs max).
" Accept exponent and mantissa information from 2 QIEs,
align the data and send the data to a gigabit serialized that
drives an optical link.
Other CCA functions include the following:
" Provide a serial interface similar to I2C for programming
_ / CCA
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al., Ray Yarema et. Channel control ASIC for the CMS hadron calorimeter front end readout module, article, September 26, 2002; Batavia, Illinois. (digital.library.unt.edu/ark:/67531/metadc742967/m1/1/: accessed November 13, 2018), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.