ISL71590SEH Datasheet, PDF (8/16 Pages) Intersil Corporation – Radiation Hardened

ISL71590SEH
support circuitry necessary with other thermal sensors such as
thermistors, thermocouples and other discrete based solutions.
External linearization circuitry, precision voltage amplifiers,
resistance measuring circuitry and cold junction compensation
are not needed when applying the ISL71590SEH.
In the simplest application, the ISL71590SEH, a resistor, a power
source and any voltmeter can be used to measure temperature.
Ideally resistors used should be of a metal film or metal strip
type, such resistors having very low thermal coefficient values.
When voltage is initially applied to the ISL71590SEH, the circuit
becomes active at slightly less than 4V, (V+ to V-), with I_OUT
ramping up typically 2µs after. There will be an initial short
period of time for the I_OUT to be correctly proportional to the
ambient temperature. Depending on the V_S ramp rate and
amplitude this may take a few µs before a reliable temperature
reading is available. See Figures 15 through 18 for scope shot
examples.
The output characteristics also makes the ISL71590SEH easy to
multiplex; with either or both the input supply voltage or the
output current can be switched by a CMOS multiplexer such as
the HS-508 or HS-1840 from Intersil.
When the ISL71590SEH die product is used, the die substrate
should be tied to the more negative of the 2 terminals for
optimum performance.
Parameter Glossary
The ISL71590SEH parametric specifications provide for an
understanding of the temperature sensor performance
over-temperature and radiation exposure. Following are critical
parameter explanations as they relate to usage and
interpretation.
Ambient Error Accuracy refers to the maximum error at an
ambient temperature of +25°C and is expressed as 0.5°C of
the Nominal Current Output at +25°C (298.15K) of 298.15µA.
The Absolute Error without External Calibration describes the
temperature accuracy over the entire -55°C to +125°C range. The
typical performance is shown in Figure 8 on page 5. Both of
these two first specification explanations are to be considered as
initial error accuracy specifications.
The Post Low Dose Rate Radiation Ambient Error (E_RADD) is the
specified accuracy after 50krad(Si) at 0.01 rad(Si) per second
(LDR) and 300krad(Si) at 70 rad(Si) per second (HDR) exposure.
This radiation hardness performance is unmatched in the
industry for this class of device, this performance is shown in
Figure 2 on page 1 as a delta over radiation type and in Figure 19
on page 7 as an absolute measurement.
Non-Linearity in referring to the ISL71590SEH, is the maximum
allowable deviation of the output current over-temperature for
any single part relative to its individual best fit line over 5 discrete
temperature (-55°C, -15°C, +25°C, +85°C, +125°C) points. This
performance is guaranteed by testing.
Repeatability Errors arise from a strain hysteresis of the
package. For the ISL71590SEH this is the maximum deviation
between +25°C readings after a single temperature excursion
between -55°C and +125°C, and is guaranteed by
characterization and is not tested. The magnitude of this error is
solely a function of the magnitude of the temperature span and
duration over which the device is exposed.
Long Term Drift Errors are related to the average operating
temperature and the magnitude of the thermal shocks
experienced by the device. Extended use of the ISL71590SEH
temperatures at +125°C typically results in long-term drift of
0.05°C after 1khr with a specification of - 0.25°C to +0.25°C.
Trimming Out Errors
The ideal graph of current versus temperature for the
ISL71590SEH is a straight line, but as Figure 20 on page 9
shows, the actual shape is slightly different (exaggerated greatly
for explanation). Since the sensor is limited to the range of -55°C
to +150°C it is possible to optimize the accuracy by trimming.
Trimming extracts the maximum performance from the sensor.
The circuit in Figure 21 on page 9 trims the slope of the
ISL71590SEH output. The effect of this is shown in Figure 22 on
page 9.
The circuit of Figure 23 on page 9 trims both the slope and the
offset.
Starting in Figure 24 on page 9 with an untrimmed slope, then
progressing through to Figure 27 on page 10 each figure showing
the effect of adjusting the offset and slope and finally the offset
again to finally arrive at an optimized condition.
The diagrams curvatures are highly are exaggerated to show
effects, but it should be clear that these trims can be used to
minimize errors over a partial or the entire temperature range.
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June 3, 2016
FN8376.2