DS1722

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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 2 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.

Temperature/Data Relationships Table 2

Address

Location

S2

6

2

5

2

4

2

3

2

2

2

1

2

0

02h

MSb

(unit =

°C)

LSb

2

-1

2

-2

2

-3

2

-4

00

00

01h

TEMPERATURE

DIGITAL OUTPUT

(BINARY)

DIGITAL OUTPUT

(HEX)

+120

°C

0111 1000 0000 0000

7800h

+25.0625

°C

0001 1001 0001 0000

1910h

+10.125

°C

0000 1010 0010 0000

0A20h

+0.5

°C

0000 0000 1000 0000

0080h

0

°C

0000 0000 0000 0000

0000h

-0.5

°C

1111 1111 1000 0000

FF80h

-10.125

°C

1111 0101 1110 0000

F5E0h

-25.0625

°C

1110 0110 1111 0000

E6F0h

-55

°C

1100 1001 0000 0000

C900h

OPERATION-Programming

The area of interest in programming the DS1722 is the Configuration register. All programming is done

via the SPI or 3-wire communication interface by selecting the appropriate address of the desired register

location. Table 3 illustrates the addresses for the two registers (configuration and temperature) of the

DS1722.

Register Address Structure Table 3

Read Address

Write Address

Active Register

00h

80h

Configuration

01h

No access

Temperature LSB

02h

No access

Temperature MSB