Datasheet
MAX31850/MAX31851
Cold-Junction Compensated, 1-Wire
Thermocouple-to-Digital Converters
23Maxim Integrated
Figure 14. Address Programming Diagram—V
DD
Powered Figure 15. Address Programming Diagram—Parasite Powered
Applications Information
Open and Shorted Thermocouple Detection
The LSB of Byte 0 in Scratchpad is normally low and
goes high if the thermocouple input is open or shorted
to ground or V
DD
. Bits 0, 1, and 2 of Byte 2 are normally
low. When bit 2 (SCV) is high, it indicates a thermocouple
short to V
DD
. When bit 1 (SCG) is high, it indicates a
thermocouple short to ground. When bit 0 (OC) is high, it
indicates a thermocouple open circuit.
Noise Considerations
Because of the small signal levels involved, thermocouple
temperature measurement is susceptible to power supply
coupled noise. The effects of power-supply noise can be
minimized by placing a 0.1FF ceramic bypass capacitor
close to the V
DD
pin of the device and to GND.
The input amplifier is a low-noise amplifier designed
to enable high-precision input sensing. Keep the
thermocouple and connecting wires away from electrical
noise sources.
It is strongly recommended to add a 10nF ceramic surface-
mount differential capacitor, placed across the T+ and
T- pins, in order to filter noise on the thermocouple lines.
MAX31850
MAX31851
AD0
AD1
AD2
AD3
DQ
LOCATION 0
AD0 = GND
AD1 = GND
AD2 = GND
AD3 = GND
V
DD
V
DD
1-Wire BUS
NOTE: AD3–AD0 CANNOT BE LEFT UNCONNECTED; EACH PIN MUST BE
CONNECTED TO EITHER V
DD
OR GND.
GND
MAX31850
MAX31851
AD0
AD1
AD2
AD3
DQ
LOCATION 1
AD0 = V
DD
AD1 = GND
AD2 = GND
AD3 = GND
V
DD
V
DD
GND
MAX31850
MAX31851
AD0
AD1
AD2
AD3
DQ
LOCATION 2
AD0 = GND
AD1 = V
DD
AD2 = GND
AD3 = GND
V
DD
V
DD
GND
MAX31850
MAX31851
AD0
AD1
AD2
AD3
DQ
LOCATION 15
AD0 = V
DD
AD1 = V
DD
AD2 = V
DD
AD3 = V
DD
V
DD
V
DD
GND
MAX31850
MAX31851
AD0
AD1
AD2
AD3
DQ
LOCATION 0
AD0 = GND
AD1 = GND
AD2 = GND
AD3 = GND
V
DD
1-Wire BUS
NOTE: AD3–AD0 CANNOT BE LEFT UNCONNECTED; EACH PIN MUST BE
CONNECTED TO EITHER DQ OR GND.
GND
MAX31850
MAX31851
AD0
AD1
AD2
AD3
DQ
LOCATION 1
AD0 = DQ
AD1 = GND
AD2 = GND
AD3 = GND
V
DD
GND
MAX31850
MAX31851
AD0
AD1
AD2
AD3
DQ
LOCATION 2
AD0 = GND
AD1 = DQ
AD2 = GND
AD3 = GND
V
DD
GND
MAX31850
MAX31851
AD0
AD1
AD2
AD3
DQ
LOCATION 15
AD0 = DQ
AD1 = DQ
AD2 = DQ
AD3 = DQ
V
DD
GND