TPS54308: Problem with TPS54308

hello,
if you touch the components during operating, the voltage or resistance will be changed at yout touching point.
Probe with oscilloscope at the touching point, and you can find the voltage change which result in unstable or stops work.

Buy resistance of finger is several hundreds kohm.
It is possible that huge resistance of finger may causes change of feedback voltage ?

In datasheet TI says that pull up resistor conected to EN pin is not necessary. However, maybe it worth to add pull up to EN ?

Peter

Hi Peter,

Please tell more details about the failure symptom. LSF or HSF damaged? If no FET damage, please check the boot cap voltage is ok or not when running the failed board, thanks.

Ryan  

Generally converter works properly and parapmeters are like in the dathasheet. But when I touch a Cbot (from 6th pin side) and a Rfb1 the controller stops work. This failure is not permanent. After that touch, controller works properly. In datasheet TI says that pull up resistor connected to A pin is not necessary. However, maybe it worth to add pull up to EN ?

Ryan Hu(MCP) said:

I don't understand the mean of your last sentence. 'Howerve, maybe it worth to add pull up to EN?'

I mean that in datasheet I have found "The EN pin has an internal pullup-current source which allows the user to float the EN pin to enable the device."

Maybe if I add some pull up resistor it helps ?

Hi Peter,

If you want to find the root cause and solution to solve this issue, please provide the waveform (Vout, SW, Vboot), so that we can know what happen when you touch the board.

Best Regards,
Shawn