Hello,
The schematic below shows an external RAM and an external Flash. Do I have to add more or remove some of the capacitors? Both RAM and Flash are connected to a PIC32MX.
Thanks!
That looks good. On the RAM just put one of each cap on each Vcc pin with the smaller value cap closest to the pin.
I didn’t get what you mean in fact:
On the FLASH there is only 1 cap with the value 100nF.
The other caps are on the RAM with 3 cap of 100nF and 1 cap of 10uF.
Sorry, I did mean the RAM not the FLASH.
I corrected my post above.
Put two of the 100nF caps very close to the two RAM Vcc pins. The other two can be a little further away but still close to the RAM chip.
Okey man thanks, so I keep the 10uF cap and don’t change it to another 100nF cap ?
Yes, the 10uF acts as a local bulk electron storage to resupply the 100nF caps when the RAM chip draws short periods of high current.
Okey man one more question for the Flash I only keep the 100nF cap or do I add another one in parallel ?
The 100nF cap on the FLASH should be enough, just be sure to place it close to the FLASH Vcc pin and ground.
When I am designing a board and am not sure if I need other parts, like caps, I’ll add the part to the schematic and a footprint on the PCB. This give me an option to easily add the part if it is found to be needed. If not I just leave the part off the PCB.