Rainbow Electronics ATtiny861_V - Manual (Page 142)

142
2588B–AVR–11/06
ATtiny261/461/861
19. ADC – Analog to Digital Converter
19.1 Features
• 10-bit Resolution
• 1.0 LSB Integral Non-linearity
• ± 2 LSB Absolute Accuracy
• 65 - 260 µs Conversion Time
• Up to 15 kSPS at Maximum Resolution
• 11 Multiplexed Single Ended Input Channels
• 16 Differential input pairs
• 15 Differential input pairs with selectable gain
• Temperature sensor input channel
• Optional Left Adjustment for ADC Result Readout
• 0 - V
CC
ADC Input Voltage Range
• Selectable 1.1V / 2.56V ADC Voltage Reference
• Free Running or Single Conversion Mode
• ADC Start Conversion by Auto Triggering on Interrupt Sources
• Interrupt on ADC Conversion Complete
• Sleep Mode Noise Cancele
• Unipolar / Bibolar Input Mode
• Input Polarity Reversal Mode
19.2 Overview
The ATtiny261/461/861 features a 10-bit successive approximation ADC. The ADC is connected
to a 11-channel Analog Multiplexer which allows 16 differential voltage input combinations and
11 single-ended voltage inputs constructed from the pins PA7..PA0 or PB7..PB4. The differential
input is equipped with a programmable gain stage, providing amplification steps of 1x, 8x, 20x or
32x on the differential input voltage before the A/D conversion. 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 19-1 .
Internal reference voltages of nominally 1.1V or 2.56V are provided On-chip. The Internal refer-
ance voltage of 2.56V, can optionally be externally decoupled at the AREF (PA3) pin by a
capacitor, for better noise performance. Alternatively, V
CC
can be used as reference voltage for
single ended channels. There is also an option to use an external voltage reference and turn-off
the internal voltage reference. These options are selected using the REFS2:0 bits of the ADMUX
control register.