Datasheet

Table Of Contents
201
2570N–AVR–05/11
ATmega325/3250/645/6450
23. Analog to Digital Converter
23.1 Features
10-bit Resolution
0.5 LSB Integral Non-linearity
± 2 LSB Absolute Accuracy
13µs - 260µs Conversion Time (50kHz to 1MHz ADC clock)
Up to 76.9kSPS at Maximum Resolution (200kHz ADC clock)
Eight Multiplexed Single Ended Input Channels
Optional Left Adjustment for ADC Result Readout
0 - V
CC
ADC Input Voltage Range
Selectable 1.1V ADC Reference Voltage
Free Running or Single Conversion Mode
ADC Start Conversion by Auto Triggering on Interrupt Sources
Interrupt on ADC Conversion Complete
Sleep Mode Noise Canceler
The Atmel ATmega325/3250/645/6450 features a 10-bit successive approximation ADC. The
ADC is connected to an 8-channel Analog Multiplexer which allows eight single-ended voltage
inputs constructed from the pins of Port F. The single-ended voltage inputs refer to 0V (GND).
The ADC contains a Sample and Hold circuit which ensures that the input voltage to the ADC is
held at a constant level during conversion. A block diagram of the ADC is shown in Figure 23-1.
The ADC has a separate analog supply voltage pin, AVCC. AV
CC
must not differ more than ±
0.3V from V
CC
. See the paragraph “ADC Noise Canceler” on page 207 on how to connect this
pin.
Internal reference voltages of nominally 1.1V or AVCC are provided On-chip. The voltage refer-
ence may be externally decoupled at the AREF pin by a capacitor for better noise performance.
The Power Reduction ADC bit, PRADC, in “Power Reduction Register” on page 37 must be dis-
abled by writing a logical zero to be able to use the ADC module.