ATmega64A
23. Analog to Digital Converter
23.1 Features
• 10-bit Resolution
• 0.75 LSB Integral Non-linearity
1.5 LSB Absolute Accuracy
•
• 13 - 260 µs Conversion Time
• Up to 15 kSPS at Maximum Resolution
• Eight Multiplexed Single Ended Input Channels
• Seven Differential Input Channels
• Two Differential Input Channels with Optional Gain of 10x and 200x
• Optional Left Adjustment for ADC Result Readout
• 0 - VCC ADC Input Voltage Range
• 2.7 - VCC Differential ADC Voltage Range
• Selectable 2.56V 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
23.2 Overview
The ATmega64A 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 device also supports 16 differential voltage input combinations. Two of the differential inputs
(ADC1, ADC0 and ADC3, ADC2) are equipped with a programmable gain stage, providing
amplification steps of 0 dB (1x), 20 dB (10x), or 46 dB (200x) on the differential input voltage
before the A/D conversion. Seven differential analog input channels share a common negative
terminal (ADC1), while any other ADC input can be selected as the positive input terminal. If 1x
or 10x gain is used, 8-bit resolution can be expected. If 200x gain is used, 7-bit resolution can be
expected.
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. AVCC must not differ more than
0.3V from VCC. See the paragraph “ADC Noise Canceler” on page 241 on how to connect this
pin.
Internal reference voltages of nominally 2.56V 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.
233
8160C–AVR–07/09
ATMEL [ ATMEL ]
