I tried to change the switching frequency by replacing Ron from 30k to 47k, then found that the frequency became around 50k, and ripple Vp-p around 200mV. Even changing back to 30k can't recover it. Is it damaged? Before it worked at around 1.2MHz normally. I have already damaged 4 pcbs.
Hello Xiao,
I hope to help you find the problem. Can you tell us the electrical specifications of the application. Such as Vin input range, Vout voltage, and minimum and maximum load current. During the early product evaluation I accidentially placed very low values of RON on the PCB and did not experience damaged devices.
Note that at low output loading the switching frequency falls when operating in discontinuous conduction mode.
Running at a frequency as high as 1.2MHz might be violating the minimum on-time of the device ( or application). But I need the electrical specs before I could answer this. What is the reason for attemting to run at such a high frequency? Best efficiency is around 400 kHz. All data sheet data taken around there.
When the boards are assembled, are the recommended thermal profiles being followed? (I think there is a new link in the data sheet on this factor.)
You can also send design files or oscilloscope shots to us at SimpleSwitcherApps@ti.com
Alan Martin TI-SVA
It should be the iron. I used a power cord without ground connection for the solder station, and was punished.