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Lt3504 Output Combination

Flo91
on Nov 24, 2020

Hi,

we use the LT3504 in a design to get four different voltages, what works great. Now I would like to reuse the design by minimal changes.

I need an output that delivers 2A instead of 1A. Does the LT3504 support connecting two outputs together for 2A output if they are at the same voltage?

(e.g. exactly same output schematic for SW4 and SW3 for 3V3, 1A; now connect the two lines together to one 3V3 out for 2A load)

Is it better to combine two outputs of the same phase or two that are 180 degrees out-of-phase? (or is both possible?)

Is a series diode in each 3V3 output necessary for this function? 

Datasheet: https://www.analog.com/media/en/technical-documentation/data-sheets/3504fa.pdf 

Thanks for your help

Flo91

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    •  Analog Employees 
    on Dec 11, 2020 8:24 PM

    Hi,

     

    Thanks for application of LT3504.

    LT3504 is not specially designed for parallel operation. The internal compensation in each channel is independent with each channel having its own duty cycle, so the current balance may not be ideal especially at start up.

    LT8602 is a very good alternative for the application.

    LT3504 can do both in-phase paralleling and the 180-degree-interleave paralleling. It depends on which channel to select. Ch2 and ch4 are in-phase with 180-degree phase different from ch3 and ch5.

    To achieve lower output voltage ripple, it is recommended to use the option with 180 degree out-of-phase. It greatly reduces the vout ripple on the same condition.

    For the series diode, I assume that it is the diode that is connected to the load in series. If that is the case, only one diode is needed for the parallel 3v3 vout.

     

    Best regards,

    Andrew

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  • 0
    •  Analog Employees 
    on Dec 11, 2020 8:24 PM

    Hi,

     

    Thanks for application of LT3504.

    LT3504 is not specially designed for parallel operation. The internal compensation in each channel is independent with each channel having its own duty cycle, so the current balance may not be ideal especially at start up.

    LT8602 is a very good alternative for the application.

    LT3504 can do both in-phase paralleling and the 180-degree-interleave paralleling. It depends on which channel to select. Ch2 and ch4 are in-phase with 180-degree phase different from ch3 and ch5.

    To achieve lower output voltage ripple, it is recommended to use the option with 180 degree out-of-phase. It greatly reduces the vout ripple on the same condition.

    For the series diode, I assume that it is the diode that is connected to the load in series. If that is the case, only one diode is needed for the parallel 3v3 vout.

     

    Best regards,

    Andrew

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