hello all.i have connected the output D0-D7 of adc0804 to a trainer board 8 LEDs.the Vcc was given 5v.I have not given any voltage to the reference voltage input.now in the analog input Vin i have given a varying voltage.when i try to see the output i was surprised.i saw either all LEDs are on or a miscombination of on-LEDs.i thoght adc will give a exact digital converted signal.after sometimes adc was not working.now i am confused that if it is because i have not given any voltage to Vref?i also want to know if there is a relation between input volrage Vin and Vref?i have varied the voltage in Vin and gave a maximum voltage of 20 volt may be.is that the reason for which adc stops converting?