Rainbow-electronics ATmega64L Bedienungsanleitung PDF herunterladen (Seite 205)

205

ATmega16(L)

2466B–09/01

Figure 106. ADC Power Connections

Offset Compensation

Schemes

The gain stage has a built-in offset cancellation circuitry that nulls the offset of differen-

tial measurements 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 subtracted in software from the measurement results. Using this

kind of software based offset correction, offset on any channel can be reduced below

one LSB.

ADC Accuracy Definitions An n-bit single-ended ADC converts a voltage linearly between GND and V

REF

in 2

steps (LSBs). The lowest code is read as 0, and the highest code is read as 2

-1.

Several parameters describe the deviation from the ideal behavior:

• Offset: The deviation of the first transition (0x000 to 0x001) compared to the ideal

transition (at 0.5 LSB). Ideal value: 0 LSB.

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

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Rainbow-electronics ATmega64L Bedienungsanleitung Seite 205