AT90PWM81 Datasheet, PDF (192/325 Pages) ATMEL Corporation – 8-bit AVR Microcontroller with 8K Bytes In- System Programmable Flash

Figure 15-2. Illustration of Vbg as a function of temperature.
1.5
BGCRR is used to move the top of the Vbg curve to the
center of the temperature range of interest
1.0
Temperature range of interest
0.5
-40 -20 -0
20
40 60
80
100
Temperature (°C)
15.4
Temperature Measurement
The temperature measurement is based on an on-chip temperature sensor that is coupled to a single ended
ADC12 channel, as shown on Figure 15-3.
Figure 15-3. Temperature sensor Circuitry
Enable when
ADEN=1
Enable when
ADC Mux=1100
VPTAT
Current-voltage
Convertor
+
-
Vtemp
BG Reefrence
ADC Mux=1100
Selecting the ADC12 channel by writing the MUX3..0 bits in ADMUX register to “1100” enables the
temperature sensor (see See “ADC Multiplexer Register – ADMUX” on page 216.). The recommended
ADC voltage reference source is the internal 2.56V voltage reference for temperature sensor measure-
ment. When the temperature sensor is enabled, the ADC converter can be used in single conversion mode
to measure the voltage over the temperature sensor. The amplifier allows to charge the ADC sample
capacitor at full CKadc clock speed. The measured voltage has a linear relationship to temperature as
192 AT90PWM81
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