Datasheet

AD7879/AD7889
Rev. C | Page 16 of 40
Temperature Calculations
If an explicit temperature reading in degrees Celsius is required,
calculate for the single-measurement method as follows:
1. Calculate the scale factor of the ADC in degrees per LSB.
Degrees per LSB = ADC LSB size/−2.1 mV =
(V
CC
/4096)/−2.1 mV
2. Save the ADC output, D
CAL
, at the calibration temperature,
T
CAL
.
3. Take the ADC reading, D
AMB
, at the temperature to be
measured, T
AMB
.
4. Calculate the difference in degrees between T
CAL
and T
AMB
by
∆T = (D
AMB
− D
CAL
) × degrees per LSB
5. Add ∆T to T
CAL
.
Example
Using V
CC
= 2.5 V as reference,
Degrees per LSB = (2.5/4096)/−2.1 × 10
−3
= −0.291
The ADC output is 983 decimal at 25°C, equivalent to a diode
forward voltage of 0.6 V.
The ADC output at T
AMB
is 880.
∆T = (880 − 983) × −0.291 = 30°C
T
AMB
= 25 + 30 = 55°C