Datasheet

190
7734Q–AVR–02/12
AT90PWM81/161
Figure 15-1. Reference circuitry.
AT90PWM81/161 has an On-chip temperature sensor for monitoring the die temperature. A volt-
age Proportional-To-Absolute-Temperature, VPTAT, is generated in the voltage reference circuit
and after buffering, is connected to the ADC multiplexer. This temperature sensor can be used
for runtime compensation of temperature drift in both the voltage reference and the On-chip
Oscillator. To get the absolute temperature in degrees Kelvin, the measured Vtemp voltage
must be scaled with the Vtemp factory calibration value stored in the signature row. See
Section “Temperature Measurement”, page 192 for details.
Vbg and Vtemp can be measured with the integrated ADC by selecting the proper ADC channel
with ADMUX (see “ADMUX - ADC Multiplexer Register” on page 217).
15.3 Register Description
15.3.1 BGCCR – Bandgap Calibration Current Register
VPTAT
REFS0, REFS1
are used to
control
SW0..3
/3.20
/2.13
/1.60
/6.40
Vref
Voltage Reference
Aref
AVcc
Vbg
ADC
Comp
BG Reference
BG Calibration
Registers
BGCCR, BGCRR
BG Calibration
Fuses
SW0
SW1
SW2
SW3
Bit 7 6543210
- - - - BGCC3 BGCC2 BGCC1 BGCC0 BGCCR
Read/Write - - - - R/W R/W R/W R/W
Initial Value 0 0 0 0 1 0 0 0