Datasheet

126
2586N–AVR–04/11
ATtiny25/45/85
17. Analog to Digital Converter
17.1 Features
• 10-bit Resolution
• 1 LSB Integral Non-linearity
• ± 2 LSB Absolute Accuracy
• 65 - 260 µs Conversion Time
• Up to 15 kSPS at Maximum Resolution
• Four Multiplexed Single Ended Input Channels
• Two differential input channels 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 / Bibilar Input Mode
• Input Polarity Reversal Mode
17.2 Overview
The ATtiny25/45/85 features a 10-bit successive approximation Analog to Digital Converter
(ADC). The ADC is connected to a 4-channel Analog Multiplexer which allows one differential
voltage input and four single-ended voltage inputs constructed from the pins of Port B. The dif-
ferential input (PB3, PB4 or PB2, PB5) is equipped with a programmable gain stage, providing
amplification step of 26 dB (20x) 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 17-1
on page 127.
Internal reference voltages of nominally 1.1V / 2.56V are provided on-chip. 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.