TPS40210: problem with Fet gate drive

Hello Soumitra,

Please share your schematic.

It seems that the device is operating with maximum duty cycle. What is your output voltage?

Please check the switch node as well.

Hi Brigitte

The schematic was within the attachment but here it is : https://e2e.ti.com/cfs-file/__key/communityserver-discussions-components-files/196/TPS40210_2D00_DER_5F00_36v_5F00_5A.pdf

The output voltage is the input voltage minus the diode drop. I dont think 2v is quite enough to drive the FET , there are no waveforms available at the inductor-diode-fet junction. 

Regards
Soumitra

Hello Soumitra,

The pdf includes the Webench result, but not the really implemented schematic, as you mentioned that you are using a different FET, I would want to get your schematic instead of the Webench result.

What is the voltage on BP? Is the problem happening on one board only? If yes, please check if a replacement of TPS40210 helps.

Hi Brigitte

The schematic i use is the same as the Webench schematic, except for the FET value. 

The voltage on BP is 7.92v so technically the IC should be working although scoping the pin shows that the voltage is not a stable flat line.

This is the only board developed and which is being tested so getting a replacement IC is going to take time. I hoped there was something else i could do to get it started. Let me try with a replacement IC. 

Thank you for your help

Regards

Soumitra

Hello Soumitra,

I just want to mention that the layout of a switch mode power supply is essential for the functionality of the converter. So if you used a breadboard to build the converter, the layout might be the root cause of the issues.