I have designed a circuit that uses an LM22678-ADJ to output 10V. I followed the datasheet strictly when designing my circuit to ensure that every component matches the specs required and that the PCB layout is the same as the layout recommended in Figure 18 of the datasheet. However, the actual output voltage measured with a voltmeter on my PCBs is approximately 2.5V. I assembled two boards to confirm this behavior. Before I order several different valued resistors to experiment swapping out the Rfbt resistor for different values, I wanted to make a post here to make sure I'm not missing a simple solution.
I understand the output voltage is set by the voltage divider made by Rfbt and Rfbb. I used the recommended 1000 ohm value for Rfbb then used the following equation from the datasheet to find the appropriate Rfbt value for output votlages greater than 5V: Rfbt = [Rfbb*(Vout-5)]/[5+Rfbb*5*10^-4]. Using Rfbb=1000 ohms and Vout=10V, I find that Rfbt should be 909 ohms. As mentioned before, my PCB layout matches the one recommended in the datasheet and all components match the specifications in the datasheet.
I would post my circuit but the software I used shows a rectangular block for each component without appropriate value labels so it would be confusing for anyone to look at.
Thanks in advance for any possible solutions.
