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

To convert a negative digital data format to temperature:

1. 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.

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 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

Table 7-3. 13-Bit Temperature Data Format

TEMPERATURE (°C)

DIGITAL OUTPUT (BINARY)

HEX

150

0 1001 0110 0000

0960

128

0 1000 0000 0000

0800

127.9375

0 0111 1111 1111

07FF

100

0 0110 0100 0000

0640

80

0 0101 0000 0000

0500

75

0 0100 1011 0000

04B0

50

0 0011 0010 0000

0320

25

0 0001 1001 0000

0190

0.25

0 0000 0000 0100

0004

0.0625

0 0000 0000 0001

0001

0

0 0000 0000 0000

0000

–0.0625

1 1111 1111 1111

1FFF

–0.25

1 1111 1111 1100

1FFC

–25

1 1110 0111 0000

1E70

–55

1 1100 1001 0000

1C90

7.3.2 Decoding Temperature Data

The TMP110 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. 2’s Complement is employed to describe negative

temperatures. C code can easily convert the 2’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, offers 0.0625°C resolution.

Table 7-4. 12-Bit Q4 Encoding Parameters

PARAMETER

VALUE

Bits

12

Q

4

Resolution

0.0625

Range (+)

127.9375

Range (–)

-128

25˚C

0x0190

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TMP110

SNIS233A – FEBRUARY 2024 – REVISED JULY 2024

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