DS1775 Datasheet, PDF (3/14 Pages) Dallas Semiconductor – SOT23-5 Digital Thermometer and Thermostat

Figure 1. Block Diagram
DS1775
OPERATION
Measuring Temperature
The core of DS1775 functionality is its direct-to-digital temperature sensor. The DS1775 measures
temperature through the use of an on-chip temperature measurement technique with an operating range
from -55°C to +125°C. Temperature conversions are initiated upon power-up, and the most recent result
is stored in the thermometer register. Conversions are performed continuously unless the user intervenes
by altering the configuration register to put the DS1775 into a shutdown mode. Regardless of the mode
used, the digital temperature can be retrieved from the temperature register by setting the pointer to that
location (00h, power-up default). The DS1775 power-up default has the sensor automatically performing
9-bit conversions continuously. Details on how to change the settings after power-up are contained in the
Programming section.
The resolution of the temperature conversion is configurable (9, 10, 11, or 12 bits), with 9-bit readings the
default state. This equates to a temperature resolution of 0.5°C, 0.25°C, 0.125°C, or 0.0625°C. Following
each conversion, thermal data is stored in the thermometer register in two’s complement format; the
information can be retrieved over the 2-wire interface with the device pointer set to the temperature
register. Table 2 describes the exact relationship of output data to measured temperature. The table
assumes the DS1775 is configured for 12-bit resolution; if the device is configured in a lower resolution
mode, those bits contain zeros. The data is transmitted serially over the 2-wire serial interface, MSb first.
The MSb of the temperature register contains the sign (S) bit, denoting whether the temperature is
positive or negative. For Fahrenheit usage, a lookup table or conversion routine must be used.
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