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LT3748 boundary mode detection

Hi, I am having some problems getting a design based on the LT3748 to regulate. The input is 12V and output should be 5V, 

Examining the scope output at the FET drain point it seems that the boundary mode condition is not being detected. The voltage at Vc pin is 740mV, so I believe the timer mentioned in the datasheet is not active.

Would this assessment be correct? Are there any adjustments I can make to the circuit?

Thank you

CH1 : FET drain

CH2: SENSE pin

CH4: GATE pin

  • Hi ted_t3r,

    Based on your schematic, it seems that your transformer has a 1:1 turns ratio. Based on the turns ratio and waveform capture, it seems the converter regulates close to 2.5V. You can check the transformer actual specs and connections, the Rfb and Rref resistors. We also suggest copying the typical application design shown on page 34 of the datasheet.

    If the problem persists, it's a good idea to contact the local FAE.