Hello
I'm having some issues with feedback resistors when trying to get 9.0V out with a 12V input.
Webench suggests using Rfb1 = 430R and Rfb2 = 330R. However this only makes Vout around 2.3V with a 12V input. To verify my connections I have tried using Rfb1 = 1k and Rfb2 = 1.5k in order to get a Vout at 3.3V and that works fine and as expected. Using the equation found in datasheet Rfb2 = (Vout/1.285-1)*Rfb1 to set 9Vout would give 6k = (9.0/1.285-1)*1k and using those resistors values, Rfb1=1k Rfb2=6k, is also confirmed and works as supposed to.
In the datasheet of the LM22675 one can read: "A good value for RFBB is 1k Ω. This will help to provide some of the minimum load current requirement and reduce susceptibility to noise pick-up.".
What my actual question is pointing towards is wether the use of lower than 1k ohm resistor in Rfb1 should work or not? My tests so far shows, as stated in datasheet, that values above 1k ohm works fine but values suggested by Webench in this case do not work at all.