since you adc is powered with

[romel emperado]

since you adc is powered with 5vdc then it is impossible to input more than 5v voltage to your adc..

 

if you want to input bigger voltage than in your Vref then you can use voltage devider for that..

 

check this tutorial and working code of adc0804:

http://adf.ly/2GyMI

 

and also check this voltage devider calculator:

 

http://adf.ly/2GyO6