ATmega88PA Automotive Atmel Corporation, ATmega88PA Automotive Datasheet - Page 145

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ATmega88PA Automotive

Manufacturer Part Number
ATmega88PA Automotive
Description
Manufacturer
Atmel Corporation
18.7.2
18.7.3
7701E–AVR–02/11
Analog Noise Canceling Techniques
ADC Accuracy Definitions
Figure 18-8. 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:
An n-bit single-ended ADC converts a voltage linearly between GND and V
(LSBs). The lowest code is read as 0, and the highest code is read as 2
Several parameters describe the deviation from the ideal behavior:
• Offset Error: The deviation of the first transition (0x000 to 0x001) compared to the ideal
Figure 18-9. Offset Error
transition (at 0.5LSB). Ideal value: 0LSB.
a. Keep analog signal paths as short as possible. Make sure analog tracks run over
b. Use the ADC noise canceller function to reduce induced noise from the CPU.
c. If any port pins are used as digital outputs, it is essential that these do not switch
the analog ground plane, and keep them well away from high-speed switching digi-
tal tracks.
while a conversion is in progress.
ADCn
Output Code
Offset
Error
Atmel ATtiny24/44/84 [Preliminary]
I
IH
I
IL
1..100 k
V
REF
Input Voltage
C
S/H
= 14 pF
Ideal ADC
Actual ADC
n
-1.
V
CC
REF
/2
in 2
n
steps
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