--- In [email protected], Thomas Treyer <[EMAIL PROTECTED]> wrote: > > Hi Geert, > > I am just wondering about your "construction", because I am designing > the schematic for my hardware. Can you please explain, why you use > the 100 Ohm series resistors? Are they necessary or are they used for > debugging purposes? > > I have some doubts about pin 12 (EXT input). In the data sheet this > pin has to be connected to either VSS or VDD. This input has high > impedance. If you leave it open, strange things may occur. The signal > level depends now on leakage current from the board and from the chip > itself. In some instances it may result in a logical Low, in other > circumstances it may be high. If this is the case, no A/D conversion > will take place. Maybe this is the problem of gazoox22. For A/D > conversion you need a clock, while you need no clock for D/A conversion. > > .................... > Thomas Treyer
Hi Thomas, The 100 Ohm resistors are there as "damping" resistors. It's a first level of protection against ESD (high voltage spikes). About your second question: you're correct. I overlooked this, since I'm using a breadboard and there are so many wires attached to the board one can hardly see the "real" hardware. Sorry for the possible misleading information... Only in case you choose to feed the clock externally, you have to connect that pin to Vcc. Gnd otherwise... Best rgds, --Geert
