Datasheet
MCP9600
DS20005426C-page 26 2015-2017 Microchip Technology Inc.
5.1.3 COLD-JUNCTION/AMBIENT
TEMPERATURE REGISTER (T
C
)
The MCP9600 integrates an ambient temperature sensor
which can be used to measure the thermocouple
cold-junction temperature. For accurate measurement,
the MCP9600 will have to be placed at close proximity to
the thermocouple cold-junction to detect the junction
ambient temperature. This is a 16-bit double-buffered,
read-only register. The temperature resolution is
user-selectable to 0.0625°C/LSb or 0.25°C/LSb
resolutions and setting the resolution determines the
temperature update rate, as shown in Table 5-2.
EQUATION 5-3: TEMPERATURE
CONVERSION
The temperature bits are in two’s complement format;
therefore, positive temperature data and negative tem-
perature data are computed differently, as shown in
Equation 5-3.
FIGURE 5-4: Thermocouple
Cold-Junction Register (T
C
) Block Diagram.
Temperature 0°C
T
C
= (UpperByte x 16 + LowerByte/16)
Temperature 0°C
T
C
= (UpperByte x 16 + LowerByte/16) – 4096
TABLE 5-2: RESOLUTION vs.
CONVERSION TIME
Resolution
Conversion
Time
(typical)
Register Bits
(Note 1:)
0.0625°C 250 ms ssss xxxx xxxx xxxx
0.25°C 63 ms ssss xxxx xxxx xx00
Note 1: ‘s’ is Sign and ‘x’ is unknown bit.
Ambient Temperature
Sensor Core
T
C
Selectable Resolution:
- 0.0625°C
-0.25°C
(see Register 5-8)
Thermocouple
Cold-Junction
Temperature –T
C
REGISTER 5-4: COLD-JUNCTION TEMPERATURE REGISTER
R-0 R-0 R-0 R-0 R-0 R-0 R-0 R-0
SIGN 128°C 64°C 32°C 16°C
bit 15 bit 8
R-0 R-0 R-0 R-0 R-0 R-0 R-0 R-0
8°C 4°C 2°C 1°C 0.5°C 0.25°C 0.125°C 0.0625°C
bit 7 bit 0
Legend:
R = Readable bit W = Writable bit U = Unimplemented bit, read as ‘0’
-n = Value at POR ‘1’ = Bit is set ‘0’ = Bit is cleared x = Bit is unknown
bit 15-12 SIGN: Sign bit
1 =T
A
0°C
0 =T
A
0°C
bit 11-0 T
C
: Data in Two’s Complement Format bits
This register contains the thermocouple cold-junction temperature or the device ambient temperature
data. Bits 1 and 0 may remain clear (‘0’) depending on the status of the Resolution register.