W. Dabrowski, Faculty of Physics and Nuclear Techniques, UMM, Cracow, Poland,
F. Anghinolfi, CERN, Geneva, Switzerland,
P. Jarron, CERN, Geneva, Switzerland,
J. Kaplon, CERN, Geneva, Switzerland,
C. Lacasta, CERN, Geneva, Switzerland,
P. Weilhammer, CERN, Geneva, Switzerland,
R. Szczygiel, Institute of Nuclear Physics, Cracow, Poland,
A. Clark, University of Geneva, Switzerland,
D. LaMarra, University of Geneva, Switzerland,
D. Macina, University of Geneva, Switzerland,
V. Cindro, Jozef Stefan Institute, Ljubljana, Slovenia,
I. Mandic, Jozef Stefan Institute, Ljubljana, Slovenia,
M. Mikuz, Jozef Stefan Institute, Ljubljana, Slovenia,
T. Dubbs, Santa Cruz Institute for Particle Physics, UCSC Santa Cruz, CA, USA,
A. Grillo, Santa Cruz Institute for Particle Physics, UCSC Santa Cruz, CA, USA,
G. Meddeler, Lawrence Berkeley National Laboratory, Berkeley, CA, USA,
H. Niggli, Lawrence Berkeley National Laboratory, Berkeley, CA, USA,
!!
The ABCD design is a single chip implementation of the binary readout
architecture for silicon strip detectors in the ATLAS Semiconductor 
Tracker. The design follows the previously developed prototype, the 
SCT128B chip. Functionally it is fully compatible with another 

technological option being developed for the SCT and employing two 
separate chips: CAFE - a front-end chip realized in the MAXIM bipolar
process, and ABC - a binary pipeline chip realized in the Honeywell 
bulk CMOS process. The DMILL technology, in which the ABCD chip has 
been fabricated, offers a possibility to implement the complete binary
architecture, as required for the ATLAS SCT, in a single chip. The
chip comprises all blocks of the binary readout architecture, the 
front-end circuitry, binary pipeline, derandomizing buffer, data 

compression logic and the readout control logic. The ABCD design has 
been manufactured successfully in an engineering run at the TEMIC 
foundry. 


The radiation hardness requirements of the ABCD chips are driven by 
the radiation levels expected in the SCT, which are 10 Mrad of 
ionizing dose and 2x10E14 of equivalent 1 MeV neutron fluence. The 
ABCD chips have been irradiated separately with X-ray, with a 50 MeV 

proton beam and with neutrons from a nuclear reactor in several steps
up to the levels as mentioned above.


The analog performance of the ABCD chip before and after irradiation 
was evaluated using a single chip test set-up. The extraction of basic
parameters, i.e. gain, noise and offset spread was obtained from 
discriminator threshold scans for various input charges. The speed of
the front-end was evaluated from a delay scan of the internal 
calibration signal. The measurements were performed for various bias 
condition of the front-end circuit, in particular for a wide range of
the bias current in the input transistor. The main observed radiation
effect in the front-end circuit is the increase of the parallel
current noise due to degradation of the current gain factor beta in 
bipolar transistors, as expected and anticipated in the design.


For detailed evaluation of the digital part of the ABCD design a 
general-purpose mixed signal tester at CERN was used. The tester 
allowed measuring the digital functionality at various clock 

frequencies and supply voltages. Based on a comprehensive evaluation 
of the digital performance of the chip some critical tests were 
identified for which we observed the speed limitations first. The 
results of these critical tests were monitored with increasing 
radiation dose. The tests were run in two modes: (a) at a constant 
supply voltage of 4 V and various (increasing) clock frequency and 
(b) at constant clock frequency of 40 MHz and decreasing 
supply 
voltage up to the points where the chips failed to respond correctly.
A global radiation effect observed in the digital circuitry was 
slowing down by about 10-20%. 


In the paper the details of radiation effects regarding the analog 
and the digital performance of the ABCD chip will be presented.


!!
The ABCD design is a single chip implementation of the binary readout 
architecture for silicon strip detectors in the ATLAS Semiconductor 
Tracker. The radiation hardness requirements of the ABCD chips are 
driven by the radiation levels expected in the SCT, which are 10 Mrad
of ionizing dose and 2x10E14 of equivalent 1 MeV neutron fluence. The
ABCD chips have been irradiated separately with X-ray, with a 50 MeV 
proton beam and with neutrons from a nuclear reactor in several steps
up to the levels as mentioned above. The details of the radiation 
effects regarding the analog and the digital performance of the chip 
will be presented and discussed.


!!