Datasheet

MAX31865
RTD-to-Digital Converter
14Maxim Integrated
RTD Resistance Registers (01h−02h)
Two 8-bit registers, RTD MSBs and RTD LSBs, contain
the RTD resistance data. The data format is shown in
Table 4. The data format is simply the 15-bit ratio of RTD
resistance to reference resistance. D0 of the RTD LSBs
register is a Fault bit that indicates whether any RTD
faults have been detected.
Table 4. RTD Resistance Registers Definition
Table 5. RTD Resistance-Data Relationship
Note: D0 (“Fault”) is assumed to be 0.
REGISTER RTD MSBS (01h) REGISTER RTD LSBS (02h) REGISTER
Bit
D7 D6 D5 D4 D3 D2 D1 D0 D7 D6 D5 D4 D3 D2 D1 D0
RTD
Resistance
Data
MSB — — — — — — — — — — — — — LSB Fault
Bit
Weighting
2
14
2
13
2
12
2
11
2
10
2
9
2
8
2
7
2
6
2
5
2
4
2
3
2
2
2
1
2
0
—
Decimal
Value
16384 8192 4096 2048 1024 512 256 128 64 32 16 8 4 2 1 —
R
RTD
/R
REF
BINARY HEX
DECIMAL
RTD MSBs (01h) RTD LSBs (02h) RTD MSBs (01h) RTD LSBs (02h)
0.025 0000 0110 0110 0110b 06h 66h 819
0.125 0010 0000 0000 0000b 20h 00h 4096
0.25 0100 0000 0000 0000b 40h 00h 8192
0.50 1000 0000 0000 0000b 80h 00h 16,384
0.75 1100 0000 0000 0000b C0h 00h 24,576
0.999 1111 1111 1111 1110b FFh FEh 32,767