Minutes of the Tracker Electronics Meeting 
July 17 2000

Present: David, Robert, Hartmut, Masa, Dieter, Vallon, and Wilko
Agenda: 
1. Wilko: results of digital-pickup testing 

Wilko presented his results of digital-pickup in layers y0 and y1 by measuring the singles 
rate in the fast-or output.  He plotted noise-hit rate versus discriminator threshold settings 
for the following three conditions: (1) Both clock and readout are inactive. (2) The clock 
is turned on at the start of readout. (3) The clock is started early and left running so that it 
is already going when the readout becomes active. His results showed that leaving the 
clock on helps a little. Robert noted that at the nominal threshold of the DAC=30, 
165mV, used in the beam test that there is little difference between the three modes. 
Hartmut commented that he is concerned that the end-of-life conditions may require the 
thresholds to be set lower. David commented that this might be just a tip of an iceberg 
problem. This may get much worse when the entire system is assembled.  Wilko’s write-
up is located here: http://scipp.ucsc.edu/groups/glast/tmp/r0_main.pdf

There was some discussion of how this might be improved by the use of Peregrine SOI, 
the idea being to take advantage of the SOI to isolate further the analog and digital 
ground returns throughout the system.  But concern was expressed that we will find out 
too late.  Robert agreed to send the existing PC board layout to Dave to review for 
possible problems that could cause coupling between digital and analog.  (Commend 
added while editing: Dave should also review the readout cable and interface-board 
designs for the same reason.)

2. Hartmut: TOT requirements 

Hartmut presented his conclusions for the requirements of Time Over Threshold, (TOT). 
He noted that all ions beyond Helium add up to less than 0.5% of the total Cosmic Ray 
flux. The dead time contribution to ions above Helium will be about 0.25% assuming that 
we have a 5kHz trigger rate and a 20uS dead-time. One application of the TOT is 
proton/electron discrimination. Hartmut stated that a signal limit of 20fC, 4 MIPs, is 
sufficient for this application.  Robert also noted that Bill Atwood was interested in 
identifying Calorimeter backsplash prongs that range out in the tracker, but no 
quantitative analysis of this issue has ever been done. The current amplifier is set to 6uS 
for one MIP and 100uS for 25 MIPs (after which it saturates).  After some discussion, we 
decided to set the amplifier TOT to be 10 MIPs = 10uS and that the Controller chip will 
time out in 20uS.  Dieter will look at the design.  He has an idea to increase the shaper 
reset current immediately after the comparator fires.

3. Dave/Dieter: new analog test chip progress/plans

Dieter reported he is making progress with Tanner. He is using the pre-amplifier files 
sent by Ned. Dieter plans to use as much of the current layout as he can for both the 
0.5um HP and the 0.5um Peregrine.  He also stated that he would look into the Peregrine 
process in the next few days. Vallon stated that it might not be easy to convert to 
Peregrine because it has different structures. Vallon stated that Peregrine might not need 
the guard bands that were used on the HP process. Robert noted that it does not hurt to 
leave them in.  It was agreed that as soon as Ned is available we will schedule a meeting 
to work out a plan for doing the layout.

4. A.O.B. 

Robert stated that he plans to use the old Clear-Event command code to make a new 
command for reading out the GTFE configuration registers.  He would like to have the 
data looped back internally to refill the register during read.  David stated that Gunther 
still prefers using a completely non-destructive readout of the configuration registers.