ATmega16A datasheet(220/352 Pages) ATMEL

220 / 352 page

220

8154B–AVR–07/09

ATmega16A

If differential channels are used, the result is

where V

POS is the voltage on the positive input pin, VNEG the voltage on the negative input pin,

GAIN the selected gain factor, and V

REF the selected voltage reference. The result is presented

in two’s complement form, from 0x200 (-512d) through 0x1FF (+511d). Note that if the user

wants to perform a quick polarity check of the results, it is sufficient to read the MSB of the result

(ADC9 in ADCH). If this bit is one, the result is negative, and if this bit is zero, the result is posi-

tive. Figure 22-14 shows the decoding of the differential input range.

Table 22-2 shows the resulting output codes if the differential input channel pair (ADCn - ADCm)

is selected with a gain of GAIN and a reference voltage of V

REF.

Figure 22-14. Differential Measurement Range

Table 22-2.

Correlation between Input Voltage and Output Codes

ADCn

Read code

Corresponding Decimal Value

VADCm + VREF/GAIN

0x1FF

511

VADCm + 511/512 VREF/GAIN

0x1FF

511

ADCm + 510/512 VREF/GAIN

0x1FE

510

ADC

VIN 1024

⋅

VREF

--------------------------

ADC

VPOS VNEG

–

() GAIN 512

⋅⋅

VREF

------------------------------------------------------------------------

Output Code

0x1FF

0x000

REF/GAIN

Differential Input

Voltage (Volts)

0x3FF

0x200

- V

REF/GAIN

ATmega16A Datasheet(PDF) 220 Page - ATMEL Corporation

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