TPS5420 don't work on new pcb design, work before

Hi Pagart,

We will likely need to see the layout and waveforms including the input voltage, output voltage and PH pin. The circuit component values and parts are identical on the new and last PCB?

If you haven't already I also recommend double checking all the component values on the new PCB to make sure everything is populated correctly. Also please analyze what has changed between the two PCBs for some ideas.

Best Regards,
Anthony

Hi, thanks for your reply.  

Please see my board layout of my new PCB.

IC5 is the TPS5420. L3 the inductor, R29/R30 the voltage diviser (vsense)

My input voltage is from lab power supply. 

I have already double check the components, old and new board have the same.

For waveform, I have old oscilloscope, I can take photo if can help ?

Best regards

A photo of the oscilloscope should help if you can get a clear one. Can you also post the last layout for reference?

Thanks, Anthony

 Here you can see my old pcb design, and this layout work

 What you need to take in picture ?

PH, Vsense, Vout ?

Thanks a lot

Here the PH pin on new pcb

and on old pcb ph pin:

 2ms/div and 10V/div

 ok

If I add Cin close to IC and move catch diode between inductance and ic is ok ?

I try to weld over the IC to validate if you answer yes :)

Thanks

On the new layout the easiest test may be to move CIN close to the catch diode, between L3 and L4. There are not many areas to move the diode for a short GND return to the CIN because the BOOT cap is in the way of the GND underneath the IC.

 I add wire between D6 and R30 ground to reduce ground return, no change.

I have another board, and Vout is 3.2V :(

Thx