Hi team,
Please check my circuit. If it is normal, there should be an oscillation at R25.
but ...
Please help to analyze it.
Best regards,
Your circuit should oscillate as shown, so long as Pin 1 of U8 is high -- however this type of oscillator is known to be unstable under some conditions. Most modern designs either use a Schmitt-trigger based oscillator or a triple inverter oscillator.
This type of oscillator design also can create voltage spikes above the absolute maximum rating of the device:
This occurs when the output of the second stage switches and the capacitor is already charged up to ~Vcc/2 resulting in ~7.5V at the input (with a 5V supply).
I would recommend to instead use an oscillator based on a single Schmitt-trigger inverter (or Schmitt-trigger input NAND gate):
The SN74LVC1G58 can be configured as a single NAND gate and has Schmitt-trigger that will allow for this type of configuration. I put together a simple oscillator from the model in the below tina-ti file:
