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A scientific study of the problems of
digital engineering for space flight systems,
with a view to their practical solution.
LAN46xx A1280A
L/C U1H359H
Total Dose Experiment - "4Strings"
Summary
The purpose of this experiment is to investigate the effect of logical state of an
internal device node during a radiation test on ICC leakage. Also, we
examine the effect of combinational macro placement on radiation effects. That is,
the difference between placing a combinational macro in a C-Module vs. the front end of an
S-Module with the flip-flop bypassed.
This special pattern has 4 strings of combinational gates controlled by a 16-state
sequential circuit; each bit of the 4-bit sequencer drives one of the four strings of
combinational logic. During the irradiation the device is kept in the home state
('0101'). The controller is cycled through all sixteen states once each hour with
the automated sequencing taking approximately 20 seconds, thus, putting the 4 strings
through all possible combinations of biases. ICC leakage is measured and
recorded for all 16 combinations of biases.
In this test of Act 2 (1.0 µm) technology, some significant effects were noticed,
although different from what was seen in SX (0.6 µm) and SX-S (0.25 µm) technology
devices. No effects have yet been seen in Act 3 (0.8 µm); note that the Act 3
pattern did not discriminate between S and C-modules. Developing ...
Date = February 2, 2001
Bias = 5VDC
Package = 172CQFP
Dose Rate = approximately 6 krad(Si)/day
Facility = GSFC
Pattern = Act2_4Strings_DUT.htm
S/N LAN171
LAN4601_5MinData.pdf
LAN4601_KFactor_Bypassed_SMod.pdf
LAN4601_KFactor_CMod.pdf
S/N LAN172
LAN4602_5min.pdf
LAN4602_bc_wc.pdf
The interesting result which is shown clearly here is that there is a difference in
response for combinational functions when placed in either the C-Module or the
combinational section of a bypassed S-Module. Additionally, unlike the SX and SX-AS
devices, the difference in current is a function of the state of the node, not whether the
state of the node changes from its "soaked" condition.
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Last Revised: January 09, 2002
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