Full resolution (JPEG) - On this page / på denna sida - On the Temperature Margins of a Transistor-Driven Coincident Current Ferrite Core Memory, by Jan-Rustan Törnquist
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Fig. 10.
Time-temperature diagram.
Fig. 11. Determination of the recommended temperature
interval at constant drive current.
Fig. 12. The [-recommended temperature-]
{+recommend-
ed tempera-
ture+} interval
at a constant
drive current
as a function
of the drive
voltage.
Fig. 13. Determination of max. temperature at temperature
compensated drive current.
Fig. It. Tmax
for
temperature compensated drive
current as a
function of
the drive
voltage.
decreases under a value when uV1 < Va and detects
as a "false zero". At 1\ the two drive current limits
are
V<//</x"
and at 7\ the limits are
h’<If<h"
In a current-temperature diagram these two limits
can be drawn as in fig. 9.
The area between the two curves indicates the
recommended drive region for reliable performance.
In a similiar way corresponding time measurements
of the output voltages, e.g. r,, Tmi and r,„ are shown
in fig. 10 at the two current limits, Ifmax and //,«;».
These diagrams have proved to be very suitable
core characteristics for marginal design.
Marginal design
With a given memory system and a given ferrite
core the drive current margins and the current-
temperature diagrams can thus be derived. In terms
of the current-temperature characteristic for
Plessey’s core S4M-F-764 temperature margins will
be determined for two different kinds of current
drives, constant current and temperature
compensated current.
Constant current
Not including the information dependable
component A I i the drive current margins at E[, = 20 V are
the same as given before.
A h = 26 mA
Fig. 11 indicates that the recommended
temperature interval is
+ 25°C < T< + 47°C
As A li depends on E/j the recommended
temperature interval can be determined for different E^
giving a result as in fig. 12.
Temperature compensated drive current
A suitable temperature compensation of the drive
current is 1.6 mA/°C. All the drive current margins
at E[, = 20 V are the same as above.
Compensations are assumed accurate within 5°C.
From fig. 13 the maximum safe temperature is
T max = 66 ° C
The lower temperature limit is given by other
considerations, e.g. maximum possible drive current
amplitude due to the transistors.
In a similar way as in fig. 12 the Tmax as a
function of the drive voltage Ej, can be determined. Such
a curve is shown in fig. 14.
Conclusions
The drive current margins in a transistor-driven
coincident current memory system are calculated
and a new ferrite core characteristic is proposed
which lends itself to marginal design of the ferrite
core memory.
Limiting factors, e.g. temperature interval, drive
voltage and maximum size of the memory can be
calculated and different kinds of current drives
compared by means of this method.
.98 ELTEKNIK 1959
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