TC7106(2002) View Datasheet(PDF) - Microchip Technology
Part Name
Description
Manufacturer
TC7106 Datasheet PDF : 26 Pages
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TC7106/A/TC7107/A
10.4 Ratiometric Resistance
Measurements
The true differential input and differential reference
make ratiometric reading possible. Typically in a ratio-
metric operation, an unknown resistance is measured,
with respect to a known standard resistance. No accu-
rately defined reference voltage is needed.
The unknown resistance is put in series with a known
standard and a current passed through the pair. The
voltage developed across the unknown is applied to the
input and the voltage across the known resistor is
applied to the reference input. If the unknown equals
the standard, the display will read 1000.
The displayed reading can be determined from the
following expression:
Displayed(Reading) = R-----U-----n----k---n----o---w-----n--x1000
RS tan dard
The display will over range for:
RUNKNOWN ≥ 2 x RSTANDARD
FIGURE 10-2:
LOW PARTS COUNT
RATIOMETRIC
RESISTANCE
MEASUREMENT
RSTANDARD
RUNKNOWN
VREF+ V+
VREF-
VIN+
TC7106A
VIN-
Analog
Common
LCD Display
FIGURE 10-3:
TEMPERATURE SENSOR
+ 9V
160kΩ
300kΩ 300kΩ
V+
V-
VIN-
1N4148
Sensor
R2
50kΩ
R1
50kΩ
VIN+
TC7106A
VFS = 2V
VREF+
VREF-
Common
FIGURE 10-4:
POSITIVE TEMPERATURE
COEFFICIENT RESISTOR
TEMPERATURE SENSOR
+ 9V
5.6kΩ
160kΩ
1N914
R1
20kΩ
0.7%/°C
PTC
R3
R2
20kΩ
V+
V-
VIN-
VIN+
TC7106A
VREF+
VREF-
Common
FIGURE 10-5:
TC7106A, USING THE
INTERNAL REFERENCE:
200mV FULL SCALE, 3
READINGS-PER-SECOND
(RPS)
To Pin 1
40
39
38
37
36
35
34
33
TC7106A
32
31
30
29
28
27
26
25
24
23
22
21
Set VREF = 100mV
100kΩ
100pF
0.1µF
0.47µF
0.22µF
1kΩ
22kΩ
1MΩ
+
0.01µF
47kΩ
IN
+–
9V
–
To Display
To Backplane
DS21455B-page 18
© 2002 Microchip Technology Inc.
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