I'm using LM3478 converter to convert 12V to 30V in standard circuit for 456kHz.
Circuit was working perfectly but when I was measuring something I demaged probably LM3478. I replaced it with new IC but it did not help. I can see after power cycle full current to R4 sensing resitor because Q1 transistor is opened via DR pin. But IC keeps it opened forever. Seems as oscillator does not work or so. I can see 2V at COMP pin (which is output of err comparator but thats all). Q1 seems correct, when I force 0V at gate it closes transistor. D1 seems correct too. FB voltage is supposed too. L1 is 6A inductor, it's heating but I don't think it's broken.
Rarely I can see that oscillator starts (I cannot repeat it) but any load causes it falls back to error state above.
Does anybody have an idea what might be wrong or what focus on? Replacing blindly IC over and over trail&error is rather strange approach.