Other Parts Discussed in Thread: TEST
I am designing a buck converter that should go from 36.5V-55V to 12V. Output current is between 20mA and 150mA. Switching frequency is 1.1 MHz, and according to the datasheet I put a 49.9k ohm resistor between RT pin and ground to set the switching frequency accordingly. I am using LTSpice to verify my design together with the unencrypted spice model provided by TI. My issue is that the switching frequency starts from 137.5kHz (one eight of the target) as expected, then goes to 275kHz, then goes to 550kHz, and then it stays there; however it should be multiplied by two again to reach the target of 1.1M Hz. In the WebBench it does reach 1.1MHz. I checked all other voltages and it looks correct. I also simulate for 5m seconds, which is more than enough to reach steady state. Is it possible that this is an issue with the model? I am attaching my schematic here.
Thank you in advance!