I am trying to design two buck boost converters based on the LTC3789 chips : Vin 10 - 35V, Vout 24V/3A and Vout 12V/2A
For the 12V converter :
- The buck-boost works well (test with no load) but won't start in the boost region (buck region ok). I assumed first that it was related to Inrush current (output filter) so I changed Css to 100nF to slow down the start but it doesn't change anyting. Any thoughts about this ?
For the 24V converter :
- The buck part works fine but not the boost part. Ith filter was initialy as stated in the LTC3789 typical application for 24V (extract from datasheet) :
I tried to change the Ith filter with values from LT power CAD but it doesn't work either. What/where should I look first ?
Thank you if you can bring some ideas on those 2 issues.