Datasheet

Note: The practical temperature ranges vary with the thermo-
couple type.
Table 2. Memory Map—Bit Weights and Functions
Table 3. Memory Map—Descriptions
Table 4. Thermocouple Temperature Data
Format
Table 5. Reference Junction Temperature
Data Format
14-BIT THERMOCOUPLE
TEMPERATURE DATA
RES
FAULT
BIT
12-BIT INTERNAL TEMPERATURE
DATA
RES
SCV
BIT
SCG
BIT
OC
BIT
BIT D31 D30 … D18 D17 D16 D15 D14 … D4 D3 D2 D1 D0
VALUE Sign
MSB 2
10
(1024°C)
…
LSB 2
-2
(0.25°C)
Reserved
1 =
Fault
Sign
MSB
2
6
(64°C)
…
LSB 2
-4
(0.0625°C)
Reserved
1 =
Short
to
V
CC
1 =
Short
to
GND
1 =
Open
Circuit
BIT NAME DESCRIPTION
D[31:18]
14-Bit Thermocouple
Temperature Data
These bits contain the signed 14-bit thermocouple temperature value. See Table 4.
D17 Reserved This bit always reads 0.
D16 Fault
This bit reads at 1 when any of the SCV, SCG, or OC faults are active. Default value
is 0.
D[15:4]
12-Bit Internal Temperature
Data
These bits contain the signed 12-bit value of the reference junction temperature. See
Table 5.
D3 Reserved This bit always reads 0.
D2 SCV Fault This bit is a 1 when the thermocouple is short-circuited to V
CC
. Default value is 0.
D1 SCG Fault This bit is a 1 when the thermocouple is short-circuited to GND. Default value is 0.
D0 OC Fault This bit is a 1 when the thermocouple is open (no connections). Default value is 0.
TEMPERATURE
(°C)
DIGITAL OUTPUT
(D[31:18])
+1600.00 0110 0100 0000 00
+1000.00 0011 1110 1000 00
+100.75 0000 0110 0100 11
+25.00 0000 0001 1001 00
0.00 0000 0000 0000 00
-0.25 1111 1111 1111 11
-1.00 1111 1111 1111 00
-250.00 1111 0000 0110 00
TEMPERATURE
(°C)
DIGITAL OUTPUT
(D[15:4])
+127.0000 0111 1111 0000
+100.5625 0110 0100 1001
+25.0000 0001 1001 0000
0.0000 0000 0000 0000
-0.0625 1111 1111 1111
-1.0000 1111 1111 0000
-20.0000 1110 1100 0000
-55.0000 1100 1001 0000
MAX31855 Cold-Junction Compensated
Thermocouple-to-Digital Converter
www.maximintegrated.com
Maxim Integrated │ 10