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LTC4353 back-to-back mosfet

Hi all,

I was wondering if LTC4353, that seems to be the doubled version of LTC4352, accept back-to-back connection for the external mosfet.

Is it possible?

The datasheet do not mention this possibility, but this is available in the little brother LTC4352.

Thank you for your help

Best regards

-Federico from Picosats

  • LTC4352 has UV/OV pins. If you have back to back diodes in the power path, using UV/OV pins, you can turn a channel off or on. LTC4353 does not have UV/OV pins. You can still do back to back diodes and then control a channel using EN pins.

  • Adding my query to the same chain as the topic is the same. 

    I tried the LTSpice model for the LTC4353 for the back to back MOSFET (n-channel) implementation. Both configurations work perfectly.

    But, I'm not clear as to how the gate drive is achieved wrt a floating source in either case.

    For example, when in CD mode, right side mosfet has a floating source pin.

    when in CS mode, the left and right side mosfet source pin is floating.

    a. I also dont see any mechanism by which this pin is sensed. 

    b. Even when the Vout pin is disconnected, the devices get turned ON.

    c. Even when the load itself is connected (assuming this is the path through which the source sees a reference in CD mode), the devices get turned ON.

    Kindly explain the turn-ON mechanism here.

  • The gate drive is achieved by a charge-pump. A similar IC using back-to-back N-FET is LTC4367.  You may check page 10 of the datasheet that explains how the FET is driven.