DS1722 Datasheet, PDF (3/14 Pages) Dallas Semiconductor – Digital Thermometer with SPI/3-Wire Interface

DS1722
OVERVIEW
A block diagram of the DS1722 is shown in Figure 1. The DS1722 consists of four major components:
1. Precision temperature sensor
2. Analog-to-digital converter
3. SPI/3-wire interface electronics
4. Data registers
The factory-calibrated temperature sensor requires no external components. The DS1722 is in a power-
conserving shutdown state upon power-up. After power-up, the user may alter the configuration register
to place the device in a continuous temperature conversion mode or in a one-shot conversion mode. In
the continuous conversion mode, the DS1722 continuously converts the temperature and stores the result
in the temperature register. As conversions are performed in the background, reading the temperature
register does not affect the conversion in progress. In the one-shot temperature conversion mode, the
DS1722 will perform one temperature conversion, store the result in the temperature register, and then
return to the shutdown state. This conversion mode is ideal for power sensitive applications. More
information on the configuration register is contained in the “OPERATION-Programming” section.
The temperature conversion results will have a default resolution of 9 bits. In applications where small
incremental temperature changes are critical, the user can change the conversion resolution from 9 bits to
8, 10, 11, or 12. This is accomplished by programming the configuration register. Each additional bit of
resolution approximately doubles the conversion time.
The DS1722 can communicate using either a Motorola Serial Peripheral Interface (SPI) or standard 3-
wire interface. The user can select either communication standard through the SERMODE pin, tying it to
V_DDD for SPI and to ground for 3-wire.
The device contains both an analog supply voltage and a digital supply voltage (V_DDA and V_DDD,
respectively). The analog supply powers the device for operation while the digital supply provides the
top rails for the digital inputs and outputs. The DS1722 was designed to be 1.8V Logic-Ready.
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