ISL71590SEH Datasheet, PDF (12/16 Pages) Intersil Corporation – Radiation Hardened

ISL71590SEH
ISL71090SEH12
1.25V
V+
12kΩ
5kΩ
402Ω
7.5kΩ
ZERO
ADJ _5kΩ
1.000V
26.1kΩ
SCALE
ADJ
15kΩ
REF HI
REF LO
ICL7106
IN HI
1kΩ
0.1%
COMMON
+
T ISL71590SEH
-
IN LO
V-
FIGURE 36. BASIC DIGITAL THERMOMETER, KELVIN SCALE WITH
ZERO ADJUST
The circuit in Figure 36 allows “zero adjustment” as well as slope
adjustment. The ISL71090SEH12 brings the input within the
common-mode range, while the 5kΩ pots trim any offset at
218K (-55°C) and set the scale factor.
Since all 3 scales have narrow V_lN spans, some optimization of
the ICL7106 components can be made to lower noise and
preserve CMR. Table 2 shows the suggested values. Similar
scaling can be used with the ICL7126 and ICL7136
(see Figures 34 through 36).
TABLE 2.
V_IN RANGE
RINT
CAZ
SCALE
(V)
(kΩ)
(µF)
K
0.223 to 0.473
220
0.47
C
-0.25 to +1.0
220
0.1
F
-0.29 to +0.996
220
0.1
FOR ALL:
C_REF = 0.1µF
C_lNT = 0.22µF
C_OSC =100pF
R_OSC = 100kΩ
+
T
-
10mV/°C
10kΩ
0.1%
1kΩ
ZERO SET
+15V
44.2kΩ
ISL70417 (¹/₄)
+
-
115kΩ
118kΩ
100Ω
20kΩ
FULL-SCALE
ADJUST
10kΩ
2.7315V
M +100mA
-
FIGURE 37. CENTIGRADE THERMOMETER (0°C TO +100°C)
Figure 37, illustrates the low bias current of the ISL70417, which
allows the use of large value gain resistors, keeping meter
current error under 0.5%. Therefore saving the expense of an
extra meter driving amplifier.
Figure 38 shows a differential temperature sensing circuit
configuration. The 50kΩ pot trims offset in the devices whether
internal or external, so it can be used to set the size of the
difference interval. This also makes it useful for liquid level
detection where there will be a measurable temperature
difference.
V+
50kΩ
(8V MIN)
V-
+
T
NO. 1 _-
5MΩ
+
T
NO. 2 _{- 10kΩ}
10kΩ
+-
V_OUT = (T₂ - T₁) x
(10mV/ °C)
ISL70417 (¹/₄)
FIGURE 38. DIFFERENTIAL THERMOMETER
In Figure 39 the reference junction(s) should be in close thermal
contact with the ISL71590SEH case. V+ must be at least 4V,
while ISL71090SEH12 current should be set 1mA to 2mA.
Calibration does not require shorting or removal of the
thermocouple: set R₁ for V₂ = 10.98mV.
If very precise measurements are needed, adjust R₂ to the exact
Seebeck coefficient for the thermocouple used (measured or
from table) note V₁ and set R₁ to buck out this voltage (i.e., set
V₂ = V₁).
For other thermocouple types, adjust values to the appropriate
Seebeck coefficient.
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June 3, 2016
FN8376.2