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LT8390 fails to start

Category: Software
Product Number: LT8390
Software Version: LT8390

hello ADI:
Recently, I designed a buck-boost circuit using our LT8390 from Analog Devices. The expected input is 12-54V and the output is 5-27V/30A. The circuit is wired and connected according to the DC2431A-4-SCH reference design, but After the circuit is built, there is no output voltage. When testing the waveforms, it is found that the BG1 pin of the main control chip LT8390 and the BG2 pin of LT8390 have positive pulse waveform output. The voltage of the TG1 pin of the main control chip LT8390 and the TG2 pin of LT8390 is always low, resulting in no output. As a troubleshooting direction, Where should I start so that the TG1 pin of the chip LT8390 and the TG2 pin of the LT8390 have a high level output?
We apologize for the extra workload caused by the doubts we encountered during use!

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  • Hello,

    Have you tried simulating the circuit?

    For a start, try checking the fault pin and other small signals if it is running correctly(intvcc), enable and such.

    Try removing the top and bot MOSFETs and see if it outputs the correct PWM.

    Regards,

    Jhun

  • 1. I re-soldered a circuit board. The parameters above are selected according to the parameters of the seat corresponding to the evaluation board DC2431 (the input power supply voltage is 24V). It can work in step-down mode, but when loaded, the output voltage is not a smooth curve, but a triangular wave with an average value of 12V, and the amplitude of the triangular wave is ±1V. When the load current is greater than 6A, the main control chip is protected and the output voltage is 0. There is a question here. The output of our evaluation board can reach 12V/25A. Why is the output of the circuit I built according to the same circuit of the evaluation board only 12V/6A? Is there a parameter in the evaluation board that was modified and not updated to the public information? Can you tell us where the parameters have been modified?
    2. I re-soldered a circuit board. The parameters above are selected according to the parameters of the seat corresponding to the evaluation board DC2431 (the input power supply voltage is 24V). By adjusting the resistors corresponding to the feedback voltage (resistors R7 R8 in the analog evaluation board DC2431), the circuit works in boost mode, and the voltage is set to 36V. However, when loaded, the output voltage is not a smooth curve, but a triangular wave with an average value of 36V, the amplitude of the triangular wave is ±3.5V, and when the load current is greater than 2A, the main control chip is protected, and the output voltage is 0 . There is a new question here. The LT8390 is a buck-boost controller, so it should also be able to work in the boost state. Why is the load capacity when I work in the boost mode significantly weaker than that in the buck mode?