Datasheet

| 25 C |- °
0.125 per Count°C
= 200 = 00C8h = 0000 1100 1000
+50 C°
0.125 per Count°C
= 400 = 0190h = 0001 1001 0000
ADS1018
SBAS526B –NOVEMBER 2012–REVISED OCTOBER 2013 www.ti.com
TEMPERATURE SENSOR
The ADS1018 temperature measurement mode is configured as a 12-bit result when enabled. Two bytes must
be read to obtain data. The first byte is the most significant byte (MSB) and is followed by a second byte, the
least significant byte (LSB). The first 12 bits are used to indicate temperature. That is, the 12-bit temperature
result is left-justified within the 16-bit result register and the last four bits always read back as '0'. One 12-bit LSB
equals 0.125°C. Negative numbers are represented in binary twos complement format.
Table 4. 12-bit Temperature Data Format
TEMPERATURE (°C) DIGITAL OUTPUT (BINARY) HEX
128 0 100 0000 0000 400
127.875 0 011 1111 1111 3FF
100 0 011 0010 0000 320
80 0 010 1000 0000 280
75 0 010 0101 1000 258
50 0 001 1001 0000 190
25 0 000 1100 1000 0C8
0.25 0 000 0000 0010 002
0 0 000 0000 0000 000
–0.25 1 111 1111 1110 FFE
–25 1 111 0011 1000 F38
–55 1 110 0100 1000 E48
Converting from Temperature to Digital Codes
For positive temperatures (for example, +50°C):
Twos complement is not performed on positive numbers. Therefore, simply convert the number to binary
code in a 12-bit, left-justified format with the MSB = 0 to denote the positive sign.
Example:
For negative temperatures (for example, –25°C):
Generate the twos complement of a negative number by complementing the absolute binary number and
adding 1. Then, denote the negative sign with the MSB = 1.
Example:
Twos complement format: 1111 0011 0111 + 1 = 1111 0011 1000
Converting from Digital Codes to Temperature
To convert from digital codes to temperature, first check whether the MSB is a '0' or a '1'. If the MSB is '0',
simply multiply the decimal code by 0.125°C to obtain the result. If the MSB = 1, subtract 1 from the result
and complement all of the bits. Then, multiply the result by –0.125°C.
Example: The ADS1018 reads back 0258h: 0258h has an MSB of '0'.
Therefore, 258h × 0.125°C = 600 × 0.125°C = +75°C
Example: The ADS1018 reads back F38h: F38h has an MSB of '1'.
Complement the result: F38h → C8h
Therefore, C8h × –0.125°C = 200 × –0.125°C = –25°C
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