TMP75B

SBOS706B – APRIL 2014 – REVISED AUGUST 2014

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7.3 Feature Description

7.3.1 Digital Temperature Output

The 12-bit digital output from each temperature measurement conversion is stored in the read-only temperature

register. Two bytes must be read to obtain the data, as shown in Figure 15. Note that byte 1 is the most

significant byte, followed by byte 2, the least significant byte. The temperature result is left-justified with the 12

most significant bits used to indicate the temperature. There is no need to read the second byte if resolution

below 1°C is not required. Table 1 summarizes the temperature data format. One LSB equals 0.0625°C.

Negative numbers are represented in binary twos complement format.

DIGITAL OUTPUT

TEMPERATURE (°C)

BINARY

HEX

128

0111 1111 1111

7FF

127.9375

0111 1111 1111

7FF

100

0110 0100 0000

640

80

0101 0000 0000

500

75

0100 1011 0000

4B0

50

0011 0010 0000

320

25

0001 1001 0000

190

0.25

0000 0000 0100

004

0

0000 0000 0000

000

–0.25

1111 1111 1100

FFC

–25

1110 0111 0000

E70

–55

1100 1001 0000

C90

(1)

The temperature sensor resolution is 0.0625°C/LSB.

Table 1 does not supply a full list of all temperatures. Use the following rules to obtain the digital data format for

a given temperature, and vice versa.

To convert positive temperatures to a digital data format:

Divide the temperature by the resolution. Then, convert the result to binary code with a 12-bit, left-justified

format, and MSB = 0 to denote a positive sign.

Example: (+50°C) / (0.0625°C / LSB) = 800 = 320h = 0011 0010 0000

To convert a positive digital data format to temperature:

Convert the 12-bit, left-justified binary temperature result, with the MSB = 0 to denote a positive sign, to a

decimal number. Then, multiply the decimal number by the resolution to obtain the positive temperature.

Example: 0011 0010 0000 = 320h = 800 × (0.0625°C / LSB) = +50°C

To convert negative temperatures to a digital data format:

Divide the absolute value of the temperature by the resolution, and convert the result to binary code with a

12-bit, left-justified format. Then, generate the twos complement of the result by complementing the binary

number and adding one. Denote a negative number with MSB = 1.

Example: (|–25°C|) / (0.0625°C / LSB) = 400 = 190h = 0001 1001 0000

Two's complement format: 1110 0110 1111 + 1 = 1110 0111 0000

To convert a negative digital data format to temperature:

Generate the twos compliment of the 12-bit, left-justified binary number of the temperature result (with MSB

= 1, denoting negative temperature result) by complementing the binary number and adding one. This

represents the binary number of the absolute value of the temperature. Convert to decimal number and

multiply by the resolution to get the absolute temperature, then multiply by –1 for the negative sign.

Example: 1110 0111 0000 has twos compliment of 0001 1001 0000 = 0001 1000 1111 + 1

Convert to temperature: 0001 1001 0000 = 190h = 400; 400 × (0.0625°C / LSB) = 25°C = (|–25°C|);

(|–25°C|) × (–1) = –25°C

8

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