Speaker
Description
Summary
At the “12th Workshop on Electronics for LHC and Future Experiments” held in
Valencia, Spain 25-29 September, 2006, we presented some results showing
operations using air core coils.
Our focus is to investigate the possibility of using DC-DC converters for the
powering of the silicon Tracker for the high luminosity ATLAS upgrade. Our
objective is to locate these regulators on the same PCB as the silicon readout
chips.
CMOS at small feature size (0.25um or less) shows promise for radiation
environments. We recently found out that at a company had designed a Buck
regulator using 0.25um CMOS technology. A device mounted on an evaluation
board with an output of 4 amps @ 1.8 Volts was exposed to Cobalt 60 source.
There was no noticeable effect even with an accumulated dosage of 100 mega
rads when the exposure was stopped (after 3 weeks of exposure). This chip is
a multichip module with a silicon die and a ferrite rod inductor. For our
application (high radiation, high magnetic field), this inductor will be replaced by
an air core coil.
We are investigating
1. Switching noise of the Buck into the silicon strip detector and its
readout chip.
2. Antenna affect, the charge from the input capacitors is transferred to
the output capacitors at a frequency of 5 MHz with a duty cycle given by output
voltage = Output voltage /Input voltage. Traces on the PC board become part
of the antenna. One solution is to bury these traces in the inner layers of the
PCB.
3. Are other vendors working on 0.25um CMOS technology Buck
regulators operating at higher frequencies?
4. More radiation testing
Figure: Power conversion Efficiency vs Output current before and after 100
Mrad Gamma exposures.
At the conference, we shall report on the results of our research.
