DS1721U Datasheet, PDF (3/17 Pages) Maxim Integrated Products – 2-Wire Digital Thermometer and Thermostat

DS1721
Each additional bit of resolution approximately doubles the conversion time, so 9-bit conversions can be
performed in less than a quarter of a second.
This is accomplished by issuing a command protocol to the configuration register. It is recommended that
the user issue the command protocol to program the configuration register before any temperature
conversion commands are issued after power-up. This is due to the fact that the configuration data is
stored in volatile memory and will always power-up in the default state. The configuration register
defines the conversion mode, thermometer resolution/conversion time, and active state of the thermostat
comparator output. It also contains 3 status bits denoting the state of temperature conversions and
thermostat flags.
The user can also program over-temperature (TH) and under-temperature (TL) setpoints for thermostatic
operation. The power-up state of TH is 80°C and that for TL is 75°C. The result of each temperature
conversion is compared with these setpoints. The thermostat output (T_OUT) becomes active when the
measured temperature exceeds the programmed TH, and remains latched in the active state until
temperature falls below TL. Thus, any hysteresis can be realized for fan control without external
components.
Digital data is written to/read from the DS1721 via a 2-wire interface, and all communication is MSb
first. Multipoint sensing is possible with the DS1721 by uniquely setting the 3-bit address of up to eight
parts on the 2-wire bus.
DS1721 FUNCTIONAL BLOCK DIAGRAM Figure 1
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