Datasheet

297
ATmega16U4/32U4 [DATASHEET]
Atmel-7766J-USB-ATmega16U4/32U4-Datasheet_04/2016
24. Analog to Digital Converter - ADC
24.1 Features
• 10/8-bit Resolution
• 0.5LSB Integral Non-linearity
• ±2LSB Absolute Accuracy
• 65 - 260µs Conversion Time
• Up to 15kSPS at Maximum Resolution
• Twelve Multiplexed Single-Ended Input Channels
• One Differential amplifier providing gain of 1x - 10x - 40x - 200x
• Temperature sensor
• 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
The ATmega16U4/ATmega32U4 features a 10-bit successive approximation ADC. The ADC is connected to an
12-channel Analog Multiplexer which allows six single-ended voltage inputs constructed from several pins of
Port B, D, and F. The single-ended voltage inputs refer to 0V (GND).
The device also supports 32 differential voltage input combinations, thanks to a differential amplifier equipped
with a programmable gain stage, providing amplification steps of 0 dB (1x), 10 dB (10x), 16dB (40x), or 23dB
(200x) on the differential input voltage before the A/D conversion. Two differential analog input channels share a
common negative terminal (ADC0/ADC1), while any other ADC input can be selected as the positive input
terminal. If 1x, 10x, or 40x 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 24-1.
The ADC has a separate analog supply voltage pin, AV
CC
. AV
CC
must not differ more than ± 0.3V from V
CC
. See
the paragraph “ADC Noise Canceler” on page 305 on how to connect this pin.
Internal reference voltages of nominally 2.56V or AV
CC
are provided On-chip. The voltage reference may be
externally decoupled at the AREF pin by a capacitor for better noise performance.