adc basic question

[kekek]

hi,
what the difference between reference voltage (vref) and maximum input voltage? as i know, vref is the maximum input voltage that the adc can measure. let say, vref for an adc is 2.0v and max. input voltage is 3.0v. if i allow 3.0v to the adc channel, is the resolution changing? what will happen if the input voltage to the adc is greater than maximum input voltage? does it harm to the adc system?

 

[Roff]

Yes, the maximum voltage spec is the maximum the part can take without damage. Any input voltage above Vref will generally give you all 1's at the output. If your input signal exceeds Vref, you will have slightly higher resolution on the signal below Vref.

 

[kekek]

ooo... that means if the input voltage is 3.0v, so the resolution is;
3.0v/2^10 = 2.9mv
where the bit size is 10.

 

[kekek]

hi,
i wrote an adc programme and i want to test it. i have a Z8 Encore! evaluation board and i loaded the mc with the programme. a multivibrator circuit which is contained a 555 timer will be connected to an adc channel. the evaluation board is supplied with 9Vdc from an adaptor while the circuit is powered with 9Vdc battery. before i proceed to the next step which is connecting the multibibrator circuit to the evaluation board, how can i make sure that there is no grounding loop or both the circut and the board are properly ground? can i simply connect the 555 timer output to the adc channel? what are the precautions that i have to take?