LTC1292 View Datasheet(PDF) - Linear Technology
Part Name
Description
MFG CO.
'LTC1292' PDF : 24 Pages View PDF
APPLICATI S I FOR ATIO
Opto-Isolated Temperature Monitor
Amplification of sensor outputs is often required to
generate a signal large enough to be properly digitized.
For example, a J-type thermocouple provides only
52µV/°C. The 5µV offset of the LTC1050 chopper op
amp generates less than 0.1°C error (Figure 31). Cold
junction compensation is provided by the LT1025A.
(For more detail see LTC Design Note 5).
In the opto-isolated interface two signals are generated
from one. This allows a two-wire interface to the
LTC1292. A long high signal (>1ms) on the CLK IN input
allows the 0.1µF capacitor to discharge taking CS high.
This resets the A/D for the next conversion. When CLK
IN starts toggling, CS goes low and stays there until the
next extended CLK IN high time. See Figure 30.
LTC1292/LTC1297
5V/DIV
CLK IN
A
CS
DATA OUT
20µs/DIV
Figure 30. Opto-Isolated Temperature
Monitor Digital Waveforms
ISOLATED
5V
+
22 µF
2k
0.1%
3.4k
0.1%
178k
0.1%
0.33µ F
LT1019-2.5
1N4148
1N4148
A 1N4148
10k
+
2
2
–
7
6
47Ω
LTC1050
LTC1292
1 CS
VCC 8
100k
2 +IN
CLK 7
0.1µ F
VIN
J
H
–
3+
+
4
LT1025A
+
1 µF
GND
R
TYPE J
4
5
+
1 µF
3 –IN
4 GND
DOUT 6
VREF 5
+
4.7µ F
74C14
1k
3Ω
0°C – 500°C TEMPERATURE RANGE
Figure 31. Opto-Isolated Temperature Monitor
4N28s
3
4
6
500k
1 5V
2 1k
CLK IN
5k
1
2
5V
3
4
6
500k
5k
DATA
OUT
LTC1292/7 F31
Information furnished by Linear Technology Corporation is believed to be accurate and reliable.
However, no responsibility is assumed for its use. Linear Technology Corporation makes no represen-
tation that the interconnection of its circuits as described herein will not infringe on existing patent rights.
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