About precision of the ADC

[sin]

Hello.

According to document IMX25AEC, there is an error of ± 2%FS in the Touchscreen ADC.

Because it is 12 bits, there is an error in 4,096* (+-0.02) = ± 82LSB.

It is very bigger than DNL and INL, is it really so?

Please tell me.

[Yuri]

The accuracy parameters of the i.MX25 integrated ADC are described in details in

the AN3948, available on the i.MX25 Documentation web page:

http://www.freescale.com/files/dsp/doc/app_note/AN3948.pdf

  The ADC accuracy is described in terms of Differential and Integral non-

linearity and referenced to the full-scale voltage that is equal to the

reference voltage. So, the ADC conversion accuracy also depends on the reference

voltage stability. The i.MX25 ADC module incorporates the reference voltage

source of 2.5V, however, it is quite inaccurate (about ± 5%). So, to achieve

maximum conversion precision, it is recommended to use an external high-

stability and low-noise reference voltage supply.