Linear Technology LTC2983 - Page 49

LTC2983
49
2983fc
For more information www.linear.com/LTC2983
Table 58. Channel Assignment Data for Differential Thermistor (44008/44032 30kΩ at 25°C Type Thermistor, Differential
Configuration, R
SENSE
on CH
11
, Auto Range Excitation)
CONFIGURATION
FIELD
DESCRIPTION # BITS BINARY DATA MEMORY
ADDRESS 0x230
MEMORY
ADDRESS 0x231
MEMORY
ADDRESS 0x232
MEMORY
ADDRESS 0x233
(1) Thermistor
Type
44008/44032
30kΩ at 25°C
5 10111 1 0 1 1 1
(2) Sense
Resistor Channel
Pointer
CH
11
5 01011 0 1 0 1 1
(3) Sensor
Configuration
Differential,
No Share,
No Rotate
3 000 0 0 0
(4) Excitation
Current
Auto Range 4 1100 1 1 0 0
Not Used Set These Bits
to 0
2 000 0 0 0
(5) Custom RTD
Data Pointer
Not Custom 12 000000000000 0 0 0 0 0 0 0 0 0 0 0 0
Table 59. Channel Assignment Data for Sense Resistor (Value = 9.99kΩ)
CONFIGURATION
FIELD
DESCRIPTION # BITS BINARY DATA MEMORY
ADDRESS 0x228
MEMORY
ADDRESS 0x229
MEMORY
ADDRESS 0x22A
MEMORY
ADDRESS 0x22B
(1) Sensor Type Sense
Resistor
5 11101 1 1 1 0 1
(2) Sense
Resistor Value
9.99kΩ 27 000100111000001100000000000 0 0 0 1 0 0 1 1 1 0 0 0 0 0 1 1 0 0 0 0 0 0 0 0 0 0 0
APPLICATIONS INFORMATION
Figure 27 shows a typical temperature measurement
system using a differential thermistor. In this example a
30kΩ (44032 type) thermistor is tied to a 9.99kΩ sense
resistor. The thermistor is assigned channel CH13 (memory
locations 0x230 to 0x233) and the sense resistor to CH11
(memory locations 0x228 to 0x22B). Channel assignment
data is shown in Tables 58 and 59).
A conversion is initiated on CH
13
by writing 10001101 into
memory location 0x000. Once the conversion is complete,
the INTERRUPT pin goes HIGH and memory location
0x000 becomes 01001101. The resulting temperature in
°C can be read from memory locations 0x040 to 0x043
(Corresponding to CH
13
).
Figure 27. Differential Thermistor Example
2983 F27
SENSE RESISTOR ASSIGNED TO CH
11
(CH
SENSE=11
)
CH
10
CHANNEL ASSIGNMENT
MEMORY LOCATIONS 0x228 TO 0x22B
CH
11
CH
12
CH
13
THERMISTOR ASSIGNED TO CH
5
(CH
THERM=13
)
CHANNEL ASSIGNMENT
MEMORY LOCATIONS 0x230 TO 0x233
RESULT MEMORY LOCATIONS 0x040 TO 0x043
R
SENSE
9.99k
100pF
100pF
TYPE 44032
100pF
2
1