ATmega169P datasheet(222/393 Pages) ATMEL

номер детали	ATmega169P

подробное описание детали	8-bit Microcontroller with 16K Bytes In-System Programmable Flash

PDF	393 Pages

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производитель	ATMEL [ATMEL Corporation]

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222

8018N–AVR–08/09

ATmega169P

22.7.1

Analog Input Circuitry

The analog input circuitry for single ended channels is illustrated in Figure 22-8. 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 k

Ω 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.

Signal components higher than the Nyquist frequency (f

ADC/2) should not be present for either

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 22-8. Analog Input Circuitry

ADCn

IIH

1..100 k

CS/H= 14 pF

VCC/2

IIL

ATmega169P датащи(PDF) 222 Page - ATMEL Corporation