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Table 7-2. 12-Bit Temperature Data Format (continued)

TEMPERATURE (°C)

DIGITAL OUTPUT (BINARY)

HEX (four LSBs are not used)

0000 0000 0000

000

-0.0625

1111 1111 1111

FFF

–0.25

1111 1111 1100

FFC

–25

1110 0111 0000

E70

–55

1100 1001 0000

C90

Table 7-2 does not list all temperatures. Use the following rules to obtain the digital data format for a given

temperature or the temperature for a given digital data format.

To convert positive temperatures to a digital data format:

1. Divide the temperature by the resolution

2. 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:

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

decimal number.

2. 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:

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

12-bit, left-justified format.

2. Generate the two’s 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:

1. Generate the two’s complement 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.

2. 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 two’s complement 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

7.3.2 Decoding Temperature Data

The TMP113 temperature registers use a 12-bit format. The 12 bits are aligned to the left side, or most

significant side, of the 16-bit word. The four unused bits are on the right side, or least significant side. For

this reason, a shift is needed to discard the extra bits. Two’s complement is employed to describe negative

temperatures. C code can easily convert the two’s complement data when the data is typecast into the correct

signed data type. Q notation describes the number of bits which represent a fractional result. 4 bits of fractional

data, known as Q4, offer 0.0625°C resolution.

Table 7-3. 12-Bit Q4 Encoding Parameters

PARAMETER

VALUE

Bits

TMP113

SBOSAJ5 – DECEMBER 2024

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