ADT7320 Data Sheet
Rev. 0 | Page 12 of 24
TEMPERATURE DATA FORMAT
One LSB of the ADC corresponds to 0.0625°C in 13-bit mode or
0.0078°C in 16-bit mode. The ADC can theoretically measure a
temperature range of 255°C, but the ADT7320 is guaranteed to
measure a low value temperature limit of −40°C to a high value
temperature limit of +150°C. The temperature measurement
result is stored in the 16-bit temperature value register and is
compared with the high temperature limits stored in the T
CRIT
setpoint register and the T
HIGH
setpoint register. It is also compared
with the low temperature limit stored in the T
LOW
setpoint register.
Temperature data in the temperature value register, the T
CRIT
setpoint register, the T
HIGH
setpoint register, and the T
LOW
setpoint register are represented by a 13-bit, twos complement
word. The MSB is the temperature sign bit. On power-up the three
LSBs, Bit 0 to Bit 2, are not part of the temperature conversion
result and are flag bits for T
CRIT
, T
HIGH
, and T
LOW
. Tabl e 5 shows
the 13-bit temperature data format without Bit 0 to Bit 2.
The number of bits in the temperature data-word can be extended
to 16 bits, twos complement by setting Bit 7 to 1 in the configuration
register (Register Address 0x01). When using a 16-bit temperature
data value, Bit 0 to Bit 2 are not used as flag bits and are instead
the LSB bits of the temperature value. The power-on default
setting has a 13-bit temperature data value.
Reading back the temperature from the temperature value register
requires a 2-byte read. Designers that use a 9-bit temperature
data format can still use the ADT7320 by ignoring the last four
LSBs of the 13-bit temperature value. These four LSBs are Bit 3
to Bit 6 in Table 5.
Table 5. 13-Bit Temperature Data Format
Temperature Digital Output (Binary) Bits[15:3]
−40°C 1 1101 1000 0000
−25°C 1 1110 0111 0000
−0.0625°C 1 1111 1111 1111
0°C 0 0000 0000 0000
+0.0625°C 0 0000 0000 0001
+25°C 0 0001 1001 0000
+105°C 0 0110 1001 0000
+125°C 0 0111 1101 0000
+150°C 0 1001 0110 0000
TEMPERATURE CONVERSION FORMULAS
16-Bit Temperature Data Format
Positive Temperature = ADC Code (dec)/128
Negative Temperature = (ADC Code (dec) − 65,536)/128
where ADC Code uses all 16 bits of the data byte, including the
sign bit.
Negative Temperature = (ADC Code (dec) − 32,768)/128
where the MSB is removed from the ADC code.
13-Bit Temperature Data Format
Positive Temperature = ADC Code (dec)/16
Negative Temperature = (ADC Code (dec) − 8192)/16
where ADC Code uses all 13 bits of the data byte, including the
sign bit.
Negative Temperature = (ADC Code (dec) − 4096)/16
where the MSB is removed from the ADC code.
10-Bit Temperature Data Format
Positive Temperature = ADC Code (dec)/2
Negative Temperature = (ADC Code (dec) − 1024)/2
where ADC Code uses all 10 bits of the data byte, including the
sign bit.
Negative Temperature = (ADC Code (dec) − 512)/2
where the MSB is removed from the ADC Code.
9-Bit Temperature Data Format
Positive Temperature = ADC Code (dec)
Negative Temperature = ADC Code (dec) − 512
where ADC Code uses all nine bits of the data byte, including
the sign bit.
Negative Temperature = ADC Code (dec) − 256
where the MSB is removed from the ADC Code.
