AT90USB646 datasheet(313/459 Pages) ATMEL

313 / 459 page

313

7593H–AVR–11/08

ATmega32U6/AT90USB64/128

25. Analog to Digital Converter - ADC

25.1

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

• Eight Multiplexed Single Ended Input Channels

• Seven Differential input channels

• Optional Left Adjustment for ADC Result Readout

• 0 - V

CC ADC Input Voltage Range

• Selectable 2.56 V 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 ATmega32U6/AT90USB64/128 features a 10-bit successive approximation ADC. The ADC

is connected 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 differential 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 differential 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 25-1.

The ADC has a separate analog supply voltage pin, AV

CC. AVCC must not differ more than ±

0.3V from VCC. See the paragraph “ADC Noise Canceler” on page 320 on how to connect this

pin.

Internal reference voltages of nominally 2.56V or AV

CC are provided On-chip. The voltage refer-

ence may be externally decoupled at the AREF pin by a capacitor for better noise performance.

AT90USB646 Datasheet(PDF) 313 Page - ATMEL Corporation