Note, the initial tests
demonstrated that an MCM can short out without affecting readout of the MCMs
closer to the TEM. However, the current
draw was higher than expected and also depended on the GTRC address. The problem was identified to be current flow
on the logic-1 address lines through the GTRC address pad input protection
diode. To rectify this we are adding
resistors to the flex-circuit cables to limit the current flow (see the latest
drawing of LAT-TD-02049). Below is a
test of this, showing that in the end the short-circuit current is consistent
with the expected polyswitch hold current.
Dear Robert,
I made the measurements we
talked about and everything works like you
expected it.
Board on pos.3 - DVDD
shorted - 1.44 A to the ground
Board on pos.1 - DVDD
shorted - 1.18 A to the ground
Board on pos.0 - DVDD
shorted - 0.62 A to the ground
Board on pos.1 - 227Ohm in
each A0 line - DVDD shorted - 0.60 A to the
ground
I tested also the
functionality. When the board on pos1 is shorted, then the
board on pos 0 is still
operable.
Marcus