Data Format
Bit D7 selects the temperature data format. When D7 is 0
(normal format), the data format is two’s complement with
a range of -128°C to (128°C - 1LSB), where the value of
an LSB depends on the resolution selection.
Write a 1 to D7 for extended temperature format. In
extended format, the MSB is given a value of 128°C,
which allows temperatures as high as 150°C to be mea-
sured. See Table 4. After changing the value of bit D7
the data format does not update until the completion of
the following temperature conversion. After setting D7 to
1, new extended temperature data is guaranteed ready
after a time equal to twice the maximum conversion time.
Note that changing the data format bit does not change
the format of the values in the T
OS
and T
HYST
registers;
these values must be written to the registers in the
current format.
Conversion Rate
The conversion rate bits, D2:D1, select the rate for auto-
matic continuous conversions. Rates of 0.25sps, 1sps,
4sps, and 8sps are available. The nominal conversion time
is 35ms at the default resolution of 10 bits. In automatic
conversion mode, a conversion is started every 4, 1, 0.25,
or 0.125 seconds, and shutdown mode is entered between
conversions to reduce average power supply current.
Shutdown
Set bit D8 to 1 to enter shutdown mode and reduce sup-
ply current to 1µA or less. If bit D8 is set to 1 when a
temperature conversion is taking place, the conversion
completes and then shutdown occurs. While in shutdown,
the I
2
C interface remains active and all registers remain
accessible to the master.
Writing 0 to D8 begins continuous conversion mode at the
rate defined by D2:D1 and starts a new conversion.
Resolution
The resolution bits (D6:D5) select the conversion reso-
lution. The conversion time doubles with every bit of
increased resolution. for example, the nominal 10-bit con-
version time is 35ms. Increasing the resolution to 12 bits
increases the conversion time to 140ms. The resolution
bits allow resolution, conversion time, and supply current
to be optimized for the application's requirements.
Fault Queue
The fault queue bits (D12:D11) select how many consecu-
tive overtemperature faults must occur before an over-
temperature fault is indicated in the Overtemperature
Status bit. The fault queue selection applies to both
Comparator and Interrupt modes. The Fault Queue does
not apply to de-asserting the over-temperature status
when the measured temperature drops below T
HYST
.
Table 5: Conversion Rate Selection
Table 6: Resolution Selection Table 7: Fault Queue Selection
D6 D5 RESOLUTION
0 0 8 bit
0 1 9 bit
1 0 10 bit (Default)
1 1 12 bit
D2 D1 CONVERSIONS/SEC
0 0 0.25 (Default)
0 1 1
1 0 4
1 1 8
D12 D11 # FAULTS
0 0 1 (Default)
0 1 2
1 0 4
1 1 6
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Maxim Integrated
│
10
MAX31875 Low-Power I
2
C Temperature
Sensor in WLP Package
