EM78P5842P Ver la hoja de datos (PDF) - ELAN Microelectronics

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Fabricante

EM78P5842P

8-BIT MICRO-CONTROLLER

ELAN Microelectronics 

EM78P5840/5841/5842

8-bit Micro-controller

EM785840’s 10 bit ADC characteristic

EM785840 build in 10 bit resolution, multi channel ADC function. In ideal, if ADC’s reference voltage is 5V, the

ADC’s LSB will be 5V/1024. But in practical, for some physics or circuit’s character, some un-ideal will effect the converter

result. As the next figure, offset voltage will reduce AD’s converter range. If AD’s input voltage less than VOFL, ADC will

output 0; in opposition, if input voltage is larger than (VDD-VOFH), ADC will output 1023. That is to say the physics AD

converter range will replace by (VDD-VOFH+LSB-VOFL+LSB). If we defined that VRB = VOFL – LSB and VRT = VDD-

VOFH+LSB, the physics LSB is:

LSB = (VRT - VRB) / 1024

= (VDD – (VOFH+VOFL) ) / 1022

For real operating, please think about the effect of AD’s offset voltage. If converter the range of (VRT - VRB), the AD

converter’s opposite result will be précised.

10-bit ADC

VDD

Min. input for ADC output = 1023

VRT

VOFH

(For 10-bit ADC, internally it takes this range to

average 1024 steps)

Min. input for ADC output = 1

0V

VOFL

VRB

Fig.19 The relative between ADC and offset voltage

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* This specification is subject to change without notice.

41

2004/11/10 V2.6

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