FS98O24 datasheet(49/77 Pages) FORTUNE

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Set AZ bit, and VIH and VIL will short. Dout will be 15625 *G * (Vio) / (VRH-VRL+Vro). It’s called Doff.

Save Doff in memory, and then Clear AZ bit to restart the ADC module.

Pass the first 2 ADC interrupts for ignoring the unstable ADC result.

When measuring analog signal, Doff should be deducted.

9.5. ADC Digital Output

The ADC digital output deducted by Doff is ADC Gain. The ADC Gain doesn’t change as VDD changes. The

suggested values for common mode voltages at ADC input and reference voltage are 1V~2V.

ADC input gain could be set by ADG[1:0] register flag. Please see Section 10.1 for detail.

9.6. ADC Resolution

ADC resolution is mainly affected by the ADC sampling counts and the ADC reference voltage. Generally

speaking, the more times ADC samples the analog input signal, the more precise the digital output is. The ADC

sampling counts could be decided by ADM[2:0] register flag. The ADC digital output rolling counts versus

ADM[2:0] and Reference voltage table are shown as follows:



(VRH, VRL) =0.4V, (VIH, VIL) =0.2V, VRL=VIL=AGND. G=1

Table 9-1 ADC rolling counts versus ADM

ADM

000

001

010

011

100

101

110

Rolling counts 10



(VRH, VRL) =VR, (VIH, VIL) =1/2 VR, VRL=VIL=AGND. G=1 ADM=101

Table 9-2 ADC rolling counts versus VR

0.05

0.1

0.2

0.3

0.4

0.6

0.8

1.0

Rolling counts 31

FS98O24 Datasheet(PDF) 49 Page - Fortune Semiconductor Corp.