Datasheet

141
8197C–AVR–05/11
ATtiny261A/461A/861A
15. ADC – Analog to Digital Converter
15.1 Features
• 10-bit Resolution
• 1.0 LSB Integral Non-linearity
• ± 2 LSB Absolute Accuracy
• 13 µs Conversion Time
• 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 / Bipolar Input Mode
• Input Polarity Reversal Mode
15.2 Overview
A 10-bit, successive approximation, Analog to Digital Converter (ADC) is connected to a 11-
channel analog multiplexer, which allows 16 differential voltage input combinations and 11 sin-
gle-ended voltage inputs constructed from the pins PA[7:0] or PB[7:4]. 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 15-1
on page 142.
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 REFS[2:0] bits of the ADC-
SRB and ADMUX registers.