DS1722

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DS1722 FUNCTIONAL BLOCK DIAGRAM

Figure 1

OPERATION-Measuring Temperature

The core of DS1722 functionality is its direct-to-digital temperature sensor. The DS1722 measures

temperature through the use of an on-chip temperature measurement technique with an operating range

from -55

° to +120°C. The device powers up in a power-conserving shutdown mode. After power-up, the

DS1722 may be placed in a continuous conversion mode or in a one-shot conversion mode. In the

continuous conversion mode, the device continuously computes the temperature and stores the most

recent result in the temperature register at addresses 01h (LSB) and 02h (MSB). In the one-shot

conversion mode, the DS1722 performs one temperature conversion and then returns to the shutdown

mode, storing temperature in the temperature register. Details on how to change the setting after power-

up are contained in the “OPERATION-Programming” section.

The resolution of the temperature conversion is configurable (8, 9, 10, 11, or 12 bits), with 9-bit readings

the default state. This equates to a temperature resolution of 1.0

°C, 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 SPI or 3-wire interface with the address set to the

temperature register, 01h (LSB) and then 02h (MSB). Table 3 describes the exact relationship of output

data to measured temperature. The table assumes the DS1722 is configured for 12-bit resolution; if the

device is configured in a lower resolution mode, those bits will contain 0s. The data is transmitted

serially over the digital interface, MSb first for SPI communication and LSb first for 3-wire

communication. 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.