ADC Module

[pascalschröer]

Hi at all,

My device: MK10DX128VLH7

I have got two questions:

1. Is there only a 12bit instead of a 16bit ADC module used? So I can only get a 16bit resolution with the help of oversampling?!

2. Can I reach the full resolution if I use an external 2.5V reference? I made some experience with the freescale S12 series and there I have to use a 3V reference to get the full resolution?!

Thanks :)

Pascal

[mjbcswitzerland]

Pascal

1. I think that you need to be careful with "resolution" and "accuracy". The ADC has 16 bit resolution but maybe not 16 bit accuracy. I believe that about 14.2 bits of accuracy is achievable when the sampling and HW averaging is optimised. Lower accuracy will be obtained when sampling is not optimised and less accuracy again if the circuitry is not well constructed to keep out noise for the power supply, references and signals.

2. Usually the ADC reference value doesn't affect resolution - Ain == VREF should always give full scale - 0xffff in 16 bit mode - the quantisation levels are simply smaller when the reference voltage is lower. But accuracy may be affected since any fixed level noise will be proportionally higher when the reference voltage is made lower.

Regards

Mark

[pascalschröer]

Hi Mark,

1. You are right, I should have say accuracy and not resolution. ;) So that point is clear.

2. Okay, I think that the effect about the noise is also clear. I have intended that there is a cpu specific fact which doesn't allow less than VCC-xV without leaving some accuracy. I have read that in a S12 datasheet, but i could find it in the kinetis datasheet.

Thank you Mark!

Pascal