Datasheet

ATmega32A

 2018 Microchip Technology Inc. Data Sheet Complete DS40002072A-page 201

23. Analog to Digital Converter

23.1 Features

• 10-bit Resolution

• 0.5 LSB Integral Non-linearity

• ±2 LSB Absolute Accuracy

• 13 - 260 µs Conversion Time

• Up to 15kSPS at Maximum Resolution

• 8 Multiplexed Single Ended Input Channels

• 7 Differential Input Channels

• 2 Differential Input Channels with Optional Gain of 10x and 200x

• Optional Left adjustment for ADC Result Readout

• 0 - V

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

23.2 Overview

The ATmega32A features a 10-bit successive approximation ADC. The ADC is connected to an 8-channel Analog

Multiplexer which allows 8 single-ended voltage inputs constructed from the pins of Port A. The single-ended volt-

age 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 23-1.

The ADC has a separate analog supply voltage pin, AVCC. AVCC must not differ more than ±0.3V from V

. See

the paragraph “ADC Noise Canceler” on page 208 on how to connect this pin.

Internal reference voltages of nominally 2.56V or AVCC are provided On-chip. The voltage reference may be exter-

nally decoupled at the AREF pin by a capacitor for better noise performance.