AT90PWM2 datasheet(241/361 Pages) ATMEL

241 / 361 page

241

4317J–AVR–08/10

AT90PWM2/3/2B/3B

Figure 21-8. Analog Input Circuitry

21.6.2

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:

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.

The AV

CC pin on the device should be connected to the digital VCC supply voltage via

an LC network as shown in Figure 21-9.

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

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 21-9. ADC Power Connections

ADCn

IIH

1..100 k

CS/H= 14 pF

VCC/2

IIL

VCC

GND

(ADC0) PE2

(ADC1) PD4

PB7(ADC4)

PB6 (ADC7)

PB5 (ADC6)

PC7 (D2A)

PB4 (AMP0+)

PB3 (AMP0-)

PC6 (ADC10/ACMP1)

AREF

AGND

AVCC

PC5 (ADC9/AMP1+)

PC4 (ADC8/AMP1-)

PB2 (ADC5)

PD7 (ACMP0)

PD6 (ADC3/ACMPM)

PD5 (ADC2/ACMP2)

100nF

Analog Ground Plane

μH

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