ADC (again) jumpy output bits @ adc 0809

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from Vref- (0 volt) and Vref+ (5 volt), it shoud be have a bit change every 0.02 volt ?

why my free running adc 0809 did not works linearly ?

when i give 0 volt, yes it shows 0000 0000 (msb-lsb),
and when i give 5 volt, it shows 1111 1111..
with this two conditions it seems works ok..


but its jumpy when reading :
(xxx are bit cheanged whenever input are not changed)
0.06 volt.. it shows 0001 0xxx
0.10 volt.. it shows 0100 1xxx
0.20 volt.. it shows 0101 0xxx

and the output has no change until 4.30 volt.. only the xxx shows different output randomly..

4.30 volt.. it shows 1001 0xxx
5.00 volt.. it shows 1111 1111

its only too sensitive from 0 until 0.05 volt,
and also too sensitive from 4.30 until 5.00 volt.

to avoid voltage jumpy, i use a Ni-Cd battery and 50K VR and 1K VR for analog input voltage (IN-0)
and computer psu for vcc and gnd.

and should i pull the unused input (IN-1 until IN-7) to gnd ?
because when i pull to gnd, my adc shows no output.. it keeps show 00000000 at 5 volt input..

and i've try with another ADC chip (but same type).. it just same jumpy..

 

[FRIED]

Possibly incorrect address. After power on take ALE low then high to latch address. Or put a RC on the pin to delay the pin going high.