Datasheet

259
4317K–AVR–03/2013
AT90PWM2/3/2B/3B
22. Digital to Analog Converter - DAC
22.1 Features
• 10 bits resolution
• 8 bits linearity
• +/- 0.5 LSB accuracy between 150mV and AVcc-150mV
• Vout = DAC*Vref/1023
• The DAC could be connected to the negative inputs of the analog comparators and/or to a
dedicated output driver.
• Output impedance around 100 Ohm.
The AT90PWM2/2B/3/3B features a 10-bit Digital to Analog Converter. This DAC can be used for the ana-
log comparators and/or can be output on the D2A pin of the microcontroller via a dedicated driver.
This allows to drive (worst case) a 1nF capacitance in parallel with a resistor higher than 33K
load with a time constant around 1us. Response time and power consumption are improved by
reducing the load (reducing the capacitor value and increasing the load resistor value (The best
case is a high impedance)).
The DAC has a separate analog supply voltage pin, AV
CC
. AV
CC
must not differ more than ±
0.3V from V
CC
. See the paragraph “ADC Noise Canceler” on page 241 on how to connect this
pin.
The reference voltage is the same as the one used for the ADC, See “ADC Multiplexer Register
– ADMUX” on page 247.. These nominally 2.56V Vref or AV
CC
are provided On-chip. The volt-
age reference may be externally decoupled at the AREF pin by a capacitor for better noise
performance.