ADC 0804 free running

Thread Starter

abhishek_h

Joined May 25, 2008
3
I connected the ADC0804 in free running mode by shorting pins 3 and 5 (INTR and WR)
now according to datasheet, initially INTR is HIGH and goes LOW after a conversion.
LOW pulse on WR is used to start the conversion.
now when i short both these pins and give a LOW pulse, it is supposed to enter running mode.
but the problem is that it remains HIGH.
even if i remove the short and give low pulse on WR, the INTR remains HIGH.

whats wrong?
 

beenthere

Joined Apr 20, 2004
15,819
The data sheet also says you have to tie chip select and read pins low. Did you do that?

The 804 should be free running after the momentary low on the write and INTR pins. Are those pins staying tied together? Do the data lines change with a changing input?
 

Thread Starter

abhishek_h

Joined May 25, 2008
3
yes i made the chip select and RD low. and i also shorted WR and INTR.
The only thing is that i did not get the required 150 pf cap for clock, so i used 100pf + 33pf + 33pf in parallel.
I also tried different combinations of resistors and capacitors.
no luck.
 
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