LM5169: Going Beyond Desired Output

Hello Bryan,

You have implemented Type2 ripple injection, but the bank of capacitors will render the loop unstable if its effective ESR is low in the mohm region.

Suggest implementing Type 3 ripple injection.

please refer to the calculator spreadsheet for Type 3 ripple injection design (COT Type III selection in spreadsheet).

SNVR520 Calculation tool | TI.com

hope this helps.

David.

Hi David, I have omitted the capacitors in my design case and it goes straight into the regulator, and the input on the regulator is still above 12V when the input voltage is higher than 12V. The output voltage is still lower than the input, but it does not stay at the intended 12V. 

Hello Bryan,

please use the calculator spreadsheet linked above, insert your specification and please post your latest schematic you are testing so I can check against the spreadsheet.  thanks.

David..

Hi David,

Thank you so much for the insight, I am including the values I used in the spreadsheet and my current schematic. 

Circuit Diagram1.pdf

hello Bryan,

you need to install a resistor in series with the COUT - use 100mR.

so it matches recommended value.

Hope this helps,

David.

I have made the changes but now its only giving me 5V output at 30V input and 2.7V output at 17.8V.

The yellow channel is the output after the inductor, and the blue channel is the value between Vfb and ground.

Hello Bryan,

please share your layout.  Thanks.

David.

I have it breadboarded for now and I apologize. If the wire lengths seem to be the issue I can try having it soldered to the perfboard that I have the chip on right now.