FARID wrote:7805 official datasheet suggest to use 0.1uF and 0.33uF but in Dendy and Famicom they used 47uF and 470uF :
I've seen different specified capacitances there, depending on the nature of the input voltage and the technology of the capacitor.
Larger capacitances are needed when you have full- (or half-) wave rectified AC and the capacitor has to hold enough power to keep everything running for up to 10ms between mains.
On the low side, a better ESR will improve AV quality.
FARID wrote:Dendy (suggests to use 470nF (=0.47uF) Electrolytic capacitor) :
Fuma (uses 100nF Ceramic capacitor) :
Famicom (suggests to use 0.47uF Electrolytic capacitor) :
so which one should I use?
On the 2A03 (I can't speak for the Dendy parts), the reset pin has a depletion NMOS pullup inside. When I measured mine, that pin emits somewhere between 20 and 50 µA continuously, only vaguely a function of the output and supply voltages.
The choice of capacitor only determines how long the CPU is held in reset after power up or after the user presses the reset button. A larger value will take longer.
The specific value doesn't seem to matter much, as long as the CPU comes out of reset consistently.
