Post by thread:[PIC] decouling capacitors for pics

I've always used a 100nf or 220nf ceramic accross each pair of power pins plus a bulk cap (electrolytic or tantalum) somewhere on the board and things seem to be fine with that (and most designs i've seen online do the same). But the recent discussion prompted me to check the 452 datasheet where I was surprised to find no mention of decoupling capacitors. Does anyone know if there are any official microchip reccomendations on what decoupling capacitors to use with PICs?

At 08:38 AM 4/17/2009, peter green wrote: >I've always used a 100nf or 220nf ceramic accross each pair of power >pins plus a bulk cap (electrolytic or tantalum) somewhere on the board >and things seem to be fine with that (and most designs i've seen online >do the same). But the recent discussion prompted me to check the 452 >datasheet where I was surprised to find no mention of decoupling capacitors. > >Does anyone know if there are any official microchip reccomendations on >what decoupling capacitors to use with PICs? No, and nor do most other micro manufacturers whose products I use. Specific recommendations are usually reserved for things like PowerPC's and ARM9's - that sort of size and speed. At the speeds you are working at generally 100nF on each supply pin plus a bulk of 22uF and upwards for the chip should be adequate. Process geometries in the PICs and similar parts are not so small as to require higher frequency bypassing. On things like FPGA's which have smaller process geometries but operate at similar clock speeds you would probably need to add a couple of 1nF to each rail (remember usually multiple rails) close to the chip. John >