LTC2983
21
2983fc
For more information www.linear.com/LTC2983
Table 13. Cold Junction Channel Pointer
(2) COLD JUNCTION CHANNEL POINTER
B26 B25 B24 B23 B22 COLD JUNCTION CHANNEL
0 0 0 0 0 No Cold Junction
Compensation, 0°C Used for
Calculations
0 0 0 0 1 CH1
0 0 0 1 0 CH2
0 0 0 1 1 CH3
0 0 1 0 0 CH4
0 0 1 0 1 CH5
0 0 1 1 0 CH6
0 0 1 1 1 CH7
0 1 0 0 0 CH8
0 1 0 0 1 CH9
0 1 0 1 0 CH10
0 1 0 1 1 CH11
0 1 1 0 0 CH12
0 1 1 0 1 CH13
0 1 1 1 0 CH14
0 1 1 1 1 CH15
1 0 0 0 0 CH16
1
0 0 0 1 CH17
1 0 0 1 0 CH18
1 0 0 1 1 CH19
1 0 1 0 0 CH20
All Other Combinations Invalid
THERMOCOUPLE MEASUREMENTS
Table 12. Thermocouple Type
(1) THERMOCOUPLE TYPE
B31 B30 B29 B28 B27 THERMOCOUPLE TYPES
0 0 0 0 1 Type J Thermocouple
0 0 0 1 0 Type K Thermocouple
0 0 0 1 1 Type E Thermocouple
0 0 1 0 0 Type N Thermocouple
0 0 1 0 1 Type R Thermocouple
0 0 1 1 0 Type S Thermocouple
0 0 1 1 1 Type T Thermocouple
0 1 0 0 0 Type B Thermocouple
0 1 0 0 1 Custom Thermocouple
Table 11. Thermocouple Channel Assignment Word
(1) THERMOCOUPLE
TYPE
(2) COLD JUNCTION
CHANNEL POINTER
(3) SENSOR
CONFIGURATION
(4) CUSTOM THERMOCOUPLE
DATA POINTER
TABLES 4, 12 TABLE 13 TABLE 14 TABLES 67 TO 69
Measurement Type 31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
Thermocouple Types 1 to 9 Cold Junction
Channel Assignment
[4:0]
SGL=1
DIFF=0
OC
Check
OC
Current
[1:0]
0 0 0 0 0 0 Custom Address
[5:0]
Custom Length –1
[5:0]
APPLICATIONS INFORMATION
sensor is assigned to (see Table 13). When a conversion
is performed on a channel tied to a thermocouple, the
cold junction sensor is simultaneously and automatically
measured. The final output data uses the embedded coef-
ficients stored in ROM to automatically compensate the
cold junction temperature and output the thermocouple
sensor temperature.
Channel Assignment – Thermocouples
For each thermocouple tied to the LTC2983, a 32-bit channel
assignment word is programmed into a memory location
corresponding to the channel the sensor is tied to (see
Table 11). This word includes (1) thermocouple type, (2)
cold junction channel pointer, (3) sensor configuration,
and (4) custom thermocouple data pointer.
(1) Thermocouple Type
The thermocouple type is determined by the first five in-
put bits B31 to B27 as shown in Table 12. Standard NIST
coefficients for types J,K,E,N,R,S,T and B thermocouples
are stored in the device ROM. If custom thermocouples
are used, the custom thermocouple sensor type can be
selected. In this case, user-specific data can be stored in
the on-chip RAM starting at the address defined in the
custom thermocouple data pointer.
(2) Cold Junction Channel Pointer
The cold junction compensation can be a diode, RTD,
or thermistor. The cold junction channel pointer tells
the LTC2983 which channel (1 to 20) the cold junction
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