DS1721

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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

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