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LT8364 / LT3094 VIOC behaviour

I am attempting to use the VIOC capability of the LT3094 to control an upstream LT8364, as shown:

This works as expected with little to no bypass capacitor on the LT3094 SET pin:

However, increasing the bypass cap (C7) to 100nF or more prevents the devices from properly starting:

Is there an error in my design / simulation, or is this a bug in either the LT3094 or LT8364?

Parents
  • Your schematic looks correct to me, but I agree the LTspice simulation does not start up correctly when there is a normally sized CSET.  My guess is that the hardware according to your schematic will work correctly, but it will take me some time to give you more conclusive input.  We have demonstration circuits available for both the LT8364 and the LT3094.  I think I will start with the LT8330 demonstration circuit since that one is already configured as a -12VOUT Cuk.  

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  • Your schematic looks correct to me, but I agree the LTspice simulation does not start up correctly when there is a normally sized CSET.  My guess is that the hardware according to your schematic will work correctly, but it will take me some time to give you more conclusive input.  We have demonstration circuits available for both the LT8364 and the LT3094.  I think I will start with the LT8330 demonstration circuit since that one is already configured as a -12VOUT Cuk.  

Children
  • Thanks ARad, reducing C2 below 300pF allows it to start up correctly but I'm not sure if there are other implications of this - the data sheet doesn't give much info on how the compensation network should be tuned.

    I also found that coupling L1 and L2 helped to clean up the oscillations.