A000047 Arduino, A000047 Datasheet - Page 286

• Manufacturer Part Number: A000047
• Description: MCU, MPU & DSP Development Tools Mega2560
• Manufacturer: Arduino
• Series: -r
• Type: MCUr

Specifications of A000047

• Processor To Be Evaluated: ATmega2560
• Interface Type: USB, I2C, SPI
• Dimensions: 4 in x 2.1 in
• Operating Supply Voltage: 5 V
• Contents: Board
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• For Use With/related Products: ATmega2560

25.6.3
25.6.4
2549M–AVR–09/10
Offset Compensation Schemes
ADC Accuracy Definitions
The stage has a built-in offset cancellation circuitry that nulls the offset of differential measure-
ments as much as possible. The remaining offset in the analog path can be measured directly by
selecting the same channel for both differential inputs. This offset residue can be then sub-
tracted in software from the measurement results. Using this kind of software based offset
correction, offset on any channel can be reduced below one LSB.
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:
•
Figure 25-11. Offset Error
•
Figure 25-12. Gain Error
Offset: The deviation of the first transition (0x000 to 0x001) compared to the ideal transition
(at 0.5 LSB). Ideal value: 0 LSB.
Gain Error: After adjusting for offset, the Gain Error is found as the deviation of the last
transition (0x3FE to 0x3FF) compared to the ideal transition (at 1.5 LSB below maximum).
Ideal value: 0 LSB.
Output Code
Output Code
Offset
Error
ATmega640/1280/1281/2560/2561
Gain
Error
V
V
REF
REF
Input Voltage
Input Voltage
Ideal ADC
Actual ADC
n
Ideal ADC
Actual ADC
-1.
REF
in 2
n
steps
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