ATmega324P datasheet(243/377 Pages) ATMEL

243 / 377 page

243

7674F–AVR–09/09

ATmega164P/324P/644P

21. ADC - Analog-to-digital Converter

21.1

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

• 8 Multiplexed Single Ended Input Channels

• Differential mode with selectable gain at 1x, 10x or 200x(1)

• Optional Left adjustment for ADC Result Readout

• 0 - V

CC ADC Input Voltage Range

• 2.7 - V

CC Differential ADC Voltage Range

• Selectable 2.56V or 1.1V 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

Note:

1. Differential Mode is not recommended above 85°C.

21.2

Overview

The ATmega164P/324P/644P features a 10-bit successive approximation ADC. The ADC is

connected to an 8-channel Analog Multiplexer which allows 8 single-ended voltage inputs con-

structed 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. This provides

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, 6-bit resolution can be

expected. Note that internal references of 1.1V should not be used on 200x gain.

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 21-1

on page 244.

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

±0.3 V from V

CC. See the paragraph “ADC Noise Canceler” on page 251 on how to connect this

pin.

Internal reference voltages of nominally 1.1V, 2.56V or AVCC are provided On-chip. The voltage

reference may be externally decoupled at the AREF pin by a capacitor for better noise

performance.

ATmega324P Datasheet(PDF) 243 Page - ATMEL Corporation

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