Rainbow-electronics ATmega32L Manual de usuario descargar pdf (Pagina 208)

100

101

208

ATmega32(L)

2503C–AVR–10/02

Figure 105. Analog Input Circuitry

Analog Noise Canceling

Techniques

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:

1. Keep analog signal paths as short as possible. Make sure analog tracks run

over the analog ground plane, and keep them well away from high-speed

switching digital tracks.

2. The AVCC pin on the device should be connected to the digital V

supply

voltage via an LC network as shown in Figure 106.

3. Use the ADC noise canceler function to reduce induced noise from the CPU.

4. If any ADC port pins are used as digital outputs, it is essential that these do

not switch while a conversion is in progress.

Figure 106. ADC Power Connections

ADCn

1..100 kΩ

S/H

= 14 pF

GND

VCC

PA0 (ADC0)

PA1 (ADC1)

PA2 (ADC2)

PA3 (ADC3)

PA4 (ADC4)

PA5 (ADC5)

PA6 (ADC6)

PA7 (ADC7)

AREF

AVCC

GND

PC7

µH

100nF

Analog Ground Plane

1 2 ... 203 204 205 206 207 208 209 210 211 212 213 ... 312 313

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Rainbow-electronics ATmega32L Manual de usuario Pagina 208

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