LT8330

According to the constraints specified in the data sheet for the LT8330, the SEPIC inverting converter voltage output can be no greater than half that of the non-inverting boost converter.  At least, this is what I read considering the limits that can be used in the FBX voltage divider resistors.

I need to generate -48V (from +12 in) and it need not supply much current - it's used in an electrostatic application.  I've already configured a design for its opposite, a +48V boost, which fits into the FBX range without any worries.  

Oddly, the LT Spice model, using the standard values on the data sheet for a -24V converter, achieves only -14.5V.

Can the LT8330 be extended to -48V out by exceeding the FBX limits and achieve a reasonably stable voltage?  (+-0.1v is fine here, plus noise).  Or, are there better solutions?

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    •  Analog Employees 
    on Feb 24, 2018 1:19 AM over 2 years ago

    Thanks for the update.

    For others who may use this post, my colleague suggested the addition of a resistor to the doubler circuit as I show below.  The resistor sometimes is needed when C4 dumps charge to C6 at the first SW turn-on.  If the combined impedance of the SW, L3, D2 and the capacitors themselves is too low, then the SW current may be high enough to hit protection the first time SW turns on, which will trigger a re-start.  Worst case is at higher VIN and constant-current load. 

     

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  • 0
    •  Analog Employees 
    on Feb 24, 2018 1:19 AM over 2 years ago

    Thanks for the update.

    For others who may use this post, my colleague suggested the addition of a resistor to the doubler circuit as I show below.  The resistor sometimes is needed when C4 dumps charge to C6 at the first SW turn-on.  If the combined impedance of the SW, L3, D2 and the capacitors themselves is too low, then the SW current may be high enough to hit protection the first time SW turns on, which will trigger a re-start.  Worst case is at higher VIN and constant-current load. 

     

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