Datasheet

MAX31865
RTD-to-Digital Converter
18Maxim Integrated
DRDY
The DRDY output goes low when a new conversion result
is available in the RTD Data Registers. When a read-
operation of the RTD Data Registers completes, DRDY
returns high.
Applications Information
For operation in noisy environments, a filter capacitor
may be placed across the RTDIN+ and RTDIN- inputs.
After an overvoltage or undervoltage fault, after a fault
detection cycle, or after enabling V
BIAS
, always allow for
the settling time of the input filter before restarting the
ADC. A delay time of at least five time constants plus an
additional 1ms (for the protection devices to stabilize) is
recommended to achieve specified accuracy.
Converting RTD Data Register
Values to Temperature
The ratiometric ADC conversion results found in the RTD
Data Registers can be converted to temperature with a
few calculations.
First, the Resistance of the RTD needs to be determined
with the following equation:
R
RTD
= (ADC Code x R
REF
)/2
15
Figure 9. DRDY Operation
SDO
RTD DATA
RTD DATA
ADDRESS
RTD REGISTER
CONTENTS
DRDY
CS
SDI
CONVERSION n CONVERSION n+1 CONVERSION n+2