how to calculate the temperature from the on-chip sensor ADC reading?
The ADuC702x has an on-chip temperature sensor. This sensor can be used to indicate the die temperature of the part. Its accuracy is typically +/-3 degree C. its reading at 25degree C is 780mV typical with a temperature coefficient of -1.3mV/degree C.
Therefore temperature can be calculated using the formula:
Temperature = (812.5-ADC reading in mV)/1.3
The LSB weight of the ADC is 2.5V/2^12 or 610uV. 780mV at 25deg C correspond to 812.5mV at 0deg C.
V = -1.3 x Temp /1000 + 812.5 mV
812.5mV is 0x533 hex
An equivalent formula is:
Temperature = 0x533 – Sensor Voltage) / 1.3