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Lt3753 and EMC noise effecting on OC pin


I use lt3753 to design 30 watts dc to dc converter.
This project is perfect .
But when this converter is exposed to emc waves, sometimes the voltage output is zero.
After doing a lot of checks on the converter, I found that OC pin of the LTC3753 chip gives a reset command due to conducted or radiate EMC noise.

That is, the sum of the noise amplitude and the voltage of the sense resistor increases from the amplitude of 96mv. This causes the fault command to be issued and the pulse of the MOSFETs to be lost.

This is due to the extraction of the OC pin from inside the chip. Increased sensitivity of the OC pin. The SNR level of the chip is extremely low. But this is not the case with the LTC3765 / 3766 chip.

Please help me

  • Hi Ali,

    If you already verified that there is no actual overcurrent event that triggers the OC then you can try to ground the OC pin to make sure that it is the OC fault that causes your output to go to zero.

    You can try adding a filter on the current sense signal similar to the standard demo board DC2306A (R10, R11, C7):

    Looking at the same schematic, you can also increase the OC threshold by adding a resistor divider (R3 and R4).


    • Hello. Thank you for your help. I have already grounded the oc pin of the chip.But the problem was not solved. I have also added a filter on the current sense signal similar DC2306A demo board. But the problem remains. The problem will only be solved if the R10 and R11 resistors from 100 ohms are converted to 2.2K ohm. But in this case, the protection against short circuit and over current is canceled. I worked with a lot of chips from ANALOGE DEVICE co. Such as AD1071, AD1074, LTC3765 / 3766, etc. But this problem only occurs in LT3753 and LT3752 chips. I think this problem arises due to the sensitivity of the OC pin and coming out of the pack. I thoroughly investigated the demo board(DC2306A),And I designed my PCB exactly according to DC2306A,But the problem still remains. The Images related to the filter section in the schematic, and the output waveform due to EMC noise are send.
  • I unfortunately can't send images for you.

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