ATMEGA128A-AUR Atmel, ATMEGA128A-AUR Datasheet - Page 240

• Manufacturer Part Number: ATMEGA128A-AUR
• Description: MCU AVR 128K FLASH 16MHZ 64TQFP
• Manufacturer: Atmel
• Series: AVR® ATmegar

Specifications of ATMEGA128A-AUR

• Core Processor: AVR
• Core Size: 8-Bit
• Speed: 16MHz
• Connectivity: EBI/EMI, I²C, SPI, UART/USART
• Peripherals: Brown-out Detect/Reset, POR, PWM, WDT
• Number Of I /o: 53
• Program Memory Size: 128KB (64K x 16)
• Program Memory Type: FLASH
• Eeprom Size: 4K x 8
• Ram Size: 4K x 8
• Voltage - Supply (vcc/vdd): 2.7 V ~ 5.5 V
• Data Converters: A/D 8x10b
• Oscillator Type: Internal
• Operating Temperature: -40°C ~ 85°C
• Package / Case: *
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

23.7.1
23.7.2
8151H–AVR–02/11
Analog Input Circuitry
Analog Noise Canceling Techniques
Note that the ADC will not be automatically turned off when entering other sleep modes than Idle
mode and ADC Noise Reduction mode. The user is advised to write zero to ADEN before enter-
ing such sleep modes to avoid excessive power consumption. If the ADC is enabled in such
sleep modes and the user wants to perform differential conversions, the user is advised to
switch the ADC off and on after waking up from sleep to prompt an extended conversion to get a
valid result.
The Analog Input circuitry for single ended channels is illustrated in Figure 23-6. An analog
source applied to ADCn is subjected to the pin capacitance and input leakage of that pin, regard-
less of whether that channel is selected as input for the ADC. When the channel is selected, the
source must drive the S/H capacitor through the series resistance (combined resistance in the
input path).
The ADC is optimized for analog signals with an output impedance of approximately 10 kΩ or
less. If such a source is used, the sampling time will be negligible. If a source with higher imped-
ance is used, the sampling time will depend on how long time the source needs to charge the
S/H capacitor, with can vary widely. The user is recommended to only use low impedant sources
with slowly varying signals, since this minimizes the required charge transfer to the S/H
capacitor.
If differential gain channels are used, the input circuitry looks somewhat different, although
source impedances of a few hundred kΩ or less is recommended.
Signal components higher than the Nyquist frequency (f
kind of channels, to avoid distortion from unpredictable signal convolution. The user is advised
to remove high frequency components with a low-pass filter before applying the signals as
inputs to the ADC.
Figure 23-6. Analog Input Circuitry
Digital circuitry inside and outside the device generates EMI which might affect the accuracy of
analog measurements. If conversion accuracy is critical, the noise level can be reduced by
applying the following techniques:
generated when the ADC conversion completes. The CPU will remain in active mode
until a new sleep command is executed.
ADCn
I
IH
I
IL
1..100 kΩ
ADC
/ 2) should not be present for either
C
S/H
ATmega128A
= 14 pF
V
CC
/2
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