Dear Team,
Could you help to check the max operation voltage in Pin 3 (R-C common) of CD4047B?
Customer finds when Vdd is 15V, the max Voltage of R-C common up to 22.5V. Could you help to check if any risk for the Pin 3 (R-C common)
Here is the schematic and waveforms tested in Pin3.
Regards,
Hi Xing,
This is normal operation for the oscillator - the RC pin is intended to handle the voltage spikes shown as long as all the other datasheet specifications are met.
These plots show the expected oscillator capacitance values -- anything larger than these could possibly cause issues.
Sure -- this works similarly to a charge pump. I can easily build such a circuit in a simulator for you to test / observe:
The capacitor (C3) cannot instantaneously change voltage, so when the output of U1 switches states, you can see that the voltage at VF1 changes by the same amount as the U1 output.
I have also attached the simulation file for Tina-TI:
