Datasheet

35
LTC2400
TYPICAL APPLICATIONS
U
V
IN
SDO
SCK
CS
3
TYPE
S
6
2
54
5V
+–
2
1
4
5
6
7
5V
10k
60Hz 50Hz
8
V
REF
V
CC
0.1µF
GND
LTC2400
F
O
2400 F36
V
IN
S
LT1025
R
–
GND
Figure 37. The LT1025 Complete Cold Junction Solution
A simpler, and potentially less expensive solution is the
use of the LT1025 as shown in Figure 37.
The LT1025 incorporates the functions of temperature
sensor, a precision divider chain required to produce the
appropriate correction for five different types of thermo-
couples, as well as curvature correction. The LT1025 must
be located at the cold junction. The use of a thermal mass
around the cold junction, as well as protection from air
currents, is advisable.
Simple Platinum RTD Interface
If high temperature resolution is required over a more
limited range, Figure 38 can resolve approximately
0.01°C without additional amplification. The resistance of
a platinum RTD changes by approximately 0.31Ω/°C at
T
A
= 25°C. The 100Ω to 300Ω source impedance of this
circuit does not compromise the stability, accuracy or
noise level of the LTC2400.
V
IN
SDO
SCK
CS
3
FS
5V
2
R1*
12.1k
Pt RTD
100Ω
1
4
*VISHAY S102 OR EQUIVALENT
5
6
7
5V
10k
60Hz 50Hz
8
V
REF
V
CC
0.1µF5V
GND
LTC2400
F
O
2400 F37
Figure 38. Simplest Platinum RTD Interface