AT90USB646 datasheet(307/456 Pages) ATMEL

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307

7593L–AVR–09/12

AT90USB64/128

26. ADC – Analog to Digital Converter

26.1

Features

• 10-bit resolution

• 0.5 LSB integral non-linearity

• ±2 LSB absolute accuracy

• 65 - 260µs conversion time

• Up to 15ksps 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 2.56V 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

26.2

Overview

The Atmel AT90USB64/128 features a 10-bit successive approximation ADC. The ADC is con-

nected to an 8-channel Analog Multiplexer which allows eight single-ended voltage inputs

constructed from the pins of Port F. 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 (1×), 20 dB (10×), or 46 dB (200×) 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 1×

or 10× gain is used, 8-bit resolution can be expected. If 200× 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 26-1

on page 308.

The ADC has a separate analog supply voltage pin, AV

CC. AVCC must not differ more than ±0.3V

from V

CC. See the paragraph “ADC noise canceler” on page 314 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) 307 Page - ATMEL Corporation

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