7.3 Feature Description

7.3.1 Digital Temperature Output

The Temp_Result registers use a 16-bit format. Temperature data is represented by a 16-bit 2's complement

word with a Least Significant Bit (LSB) equal to 0.0078125°C. The fractional values are included in the

temperature readings, which can be denoted using Q notation, a simple way to represent the length of the

fractional portion of the value. 2's Compliment is employed to describe negative temperatures. C code can easily

convert the 2's Compliment data when the data is typecast into the correct signed data type. For more details

on using Q notation to decode digital temperature data, refer to How to Read and Interpret Digital Temperature

Sensor Output Data (SBAA588).

Note following power-up or reset, the temperature register reads 0°C until the first conversion is complete. Also

note the decoding scheme allows temperature measurement beyond the recommended operating temperature

range of -40°C to 125°C, but the device performance is not guaranteed beyond this range.

Table 7-1. Encoding Parameters

Parameter

Value

Bits

16

Q

7

Resolution

0.0078125

Range (+)

255.9921875

Range (-)

-256

25˚C

0xC80

Table 7-2. 16-Bit Q Notation Bit Weights

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

Sign

128

64

32

16

8

4

2

1

0.5

0.25

0.125 0.0625

0.0312

5

0.0156

25

0.0078

125

-256

128

64

32

16

8

4

2

1

1/2

1/4

1/8

1/16

1/32

1/64

1/128

-28

27

26

25

24

23

22

21

20

2-1

2-2

2-3

2-4

2-5

2-6

2-7

C Code Examples:

/* 16-bit format will have 0 bits discarded by right shift

q7 is 0.0078125 resolution

the following bytes represent 24.5C */

uint8_t byte1 = 0xC;

uint8_t byte2 = 0x40;

float f = ((int8_t) byte1 << 8 | byte2) * 0.0078125f;

int mC = ((int8_t) byte1 << 8 | byte2) * 1000 >> 7;

int C = ((int8_t) byte1 << 8 | byte2) >> 7;

Table 7-3 shows some example temperatures and the converted register values in binary and hexadecimal

format.

Table 7-3. 16-Bit Temperature Data Format

TEMPERATURE (°C)(1)

DIGITAL OUTPUT (BINARY)

HEX

125

0011 1110 1000 0000

3E80

100

0011 0010 0000 0000

3200

80

0010 1000 0000 0000

2800

75

0010 0101 1000 0000

2580

50

0001 1001 0000 0000

1900

25

0000 1100 1000 0000

0C80

0.25

0000 0000 0010 0000

0020

0.0625

0000 0000 0000 1000

0008

TMP118

SNIS237 – DECEMBER 2024

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