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TPS62135: Issue with VFB being different, which makes the circuit output a different voltage

Part Number: TPS62135

Hello:

7V4_BUCK_WBDesign106.pdf

We used Webench to design a 7.4V buck converter using the TPS62135RGXR. We used the schematic as shown in the webench design (attached) and verified that the schematic and layout are correct. We also checked that the results from Webench are correct, which they seem so.

However we received some test boards today and we are seeing a higher output voltage than expected. I have checked that all components are what we expect them to be, to rule out any BOM error.

I did notice however measuring the voltage from Vfb that the voltage we got was ~1V rather than the 0.7V from the datasheet.

With Eq. 16 of datasheet (10.2.1.2) 0.7V, R1=953K, R2=100K, we get our desired voltage of 7.4v, as Webench designed.

However, we are getting an output of 11.13V, with a VFB of ~1.046V . Doing the same feedback equation with this new Vfb, we do get that the system should be outputing sais voltage. My question is though, why is VFB not 0.7V? I suspect it might be something with the SS/TR pin (its voltage is 2.189V. But this pin only has a 2.2nF capacitor (thiso ne: https://www.digikey.com/en/products/detail/yageo/CC0402KRX7R8BB222/5195616