Roff
Well-Known Member
The charge on the capacitor can't change instantaneously, which means the voltage across it can't change instantaneously. In your series RC circuit, if you put a very fast step of voltage on the power supply pin, the voltage on the other terminal on the cap will therefore change suddenly also. If the cap was initially uncharged (zero volts across it), the pin connected to the resistor will suddenly jump to the same voltage as the power supply. However, if the supply voltage now stays high, the cap will charge through the resistor until it is fully charged, at which time the voltage across the resistor is zero. So, you created a reset pulse to Vcc, and then the voltage returned to zero, releasing the reset condition.shaneshane1 said:Confused a little , so does this mean that the capacitors negative pin is +V until the cap is charged?
In the real world, if the power supply risetime is not extremely fast, the cap will be charging while the power supply voltage is rising, resulting in a waveform like the ones I posted above.