at90pwm81-16se ATMEL Corporation, at90pwm81-16se Datasheet - Page 211

• Manufacturer Part Number: at90pwm81-16se
• Description: 8-bit Avr Microcontroller With 8k Bytes In- System Programmable Flash
• Manufacturer: ATMEL Corporation

18.6.2
18.6.3
7734M–AVR–03/10
Analog Noise Canceling Techniques
Offset Compensation Schemes
Figure 18-8.
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:
Figure 18-9.
The gain stage has a built-in offset cancellation circuitry that nulls the offset of differential measurements
as much as possible. The remaining offset in the analog path can be measured directly by shortening both
a.
b.
c.
d.
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
LC network as shown in
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.
Analog Input Circuitry
ADC Power Connections
CC
pin on the device should be connected to the digital V
VCC
GND
ADCn
Figure
18-9.
I
IH
I
IL
Analog Ground Plane
1..100 kΩ
AVCC
AREF
AGND
C
S/H
= 14 pF
CC
supply voltage via an
AT90PWM81
V
CC
/2
100nF
10 µH
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