DS75

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DS75 FUNCTIONAL BLOCK DIAGRAM Figure 1

OPERATION–Measuring Temperature

The core of DS75 functionality is its direct–to–digital temperature sensor. The DS75 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 DS75 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 DS75 power–up default has the sensor automatically performing

9–bit conversions continuously. Details on how to change the settings after pow-er up are contained in the

“OPERATION– 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 DS75 is configured for 12–bit resolution; if the device is configured in a lower

resolution mode, those bits will 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.