Datasheet

206
ATmega8535(L)
2502K–AVR–10/06
Analog-to-Digital
Converter
Features • 10-bit Resolution
• 0.5 LSB Integral Non-linearity
• ±2 LSB Absolute Accuracy
• 65 - 260 µs Conversion Time
• Up to 15 kSPS at Maximum Resolution
• 8 Multiplexed Single Ended Input Channels
• 7 Differential Input Channels
• 2 Differential Input Channels with Optional Gain of 10x and 200x
(1)
• Optional Left Adjustment for ADC Result Readout
• 0 - V
CC
ADC Input 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
Note: 1. The differential input channel are not tested for devices in PDIP and PLCC Package.
This feature is only guaranteed to work for devices in TQFP and QFN/MLF Packages.
The ATmega8535 features a 10-bit successive approximation ADC. The ADC is con-
nected to an 8-channel Analog Multiplexer which allows eight single-ended voltage
inputs constructed from the pins of Port A. The single-ended voltage inputs refer to 0V
(GND).
The device also supports 16 differential voltage input combinations. Two of the differen-
tial 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 dif-
ferential 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 98.
The ADC has a separate analog supply voltage pin, AVCC. AVCC must not differ more
than ±0.3V from V
CC
. See the paragraph “ADC Noise Canceler” on page 214 on how to
connect this pin.
Internal reference voltages of nominally 2.56V or AVCC are provided On-chip. The volt-
age reference may be externally decoupled at the AREF pin by a capacitor for better
noise performance.