Original question:
I'M so sorry to reply so late.
we check the wave about SW, we found the wave of SW seems unnormal as below picture
we force the mode pin to Vin and the IC should be work in PWM mode,
but the the fsw change from 3M to 1.37MHz and it change all the time.
You can also see that there is a period of time when SW is always high.
please help us to clear why the fsw change when in PWM mode?
this questiom is a related question to following question.
Hi Lin,
Thanks for getting back. It seems to me a noise problem in the system like mentioned in the previous thread. Reducing the values of the feedback resistor sometimes help reduce the effect of noise. Can you recheck if you still have the problem if you reduce the FB resistors (R4007, R4006 and R4004) by one decade, so that the values are 470Ohm, 16K and 75K. After checking this can you also try without the C4003?
Best regards,
Varun
