My design information is below.
Input voltage: 5V
Output voltage: 2V
Output current: about 500mA
Schematic as below attached.
When I measure the voltage of the FB pin, or lay a finger or any other conductor (such as the probe of oscilloscope) on this pin, it will work abnormally.
I have done some change such as change the mode to fix frenquency mode, add input and output cap, decrease the FB up and down res, but the issue is still as before.
I have test the PWM waveform when fix frenquecy mode or power save mode, the PWM signal is not very stable.
Do you have some suggestion about it ?