ADC 0804 free running

Discussion in 'General Electronics Chat' started by abhishek_h, May 25, 2008.

  1. abhishek_h

    Thread Starter New Member

    May 25, 2008
    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?
  2. beenthere

    Retired Moderator

    Apr 20, 2004
    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?
  3. abhishek_h

    Thread Starter New Member

    May 25, 2008
    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.