LTC4015 reduced parts count

Hi I have been using the LTC4015 in my products for several years now and find it to be an excellent part.  I have a new application and would like to keep using the LTC4015 to reduce inventory and increase purchase quantities.

My new application does not require the Power Path functionality, i.e. the system is not powered from the SYS output, also the coulomb counter is not required, how many parts from the evaluation schematic can be eliminated, i.e. do I need the OUTFET OR THE INFET, do I need all the SYS filter capacitors?  Can some of the FETs be replaced by diodes?

Your assistance is appreciated.

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    •  Analog Employees 
    on Feb 12, 2021 7:38 PM

    Hello,

    Glad to hear LTC4015 is working well for you!

    Understood about purchase quantities, but since you don't need the coulomb counter I should at least make you aware of the LTC4162 which has nearly the same capabilities of the LTC4015 (except the coulomb counter) and is significantly cheaper - so you decide if it is worth it. Just note that it is a monolithic buck, so the charge current is limited to 3.2A (unlike the LTC4015).

    INFET and OUTFET both serve necessary roles even if the SYS rail is not used. You CAN replace them with diodes, but I do not recommend omitting them. The attached document gives a little explanation for OUTFET, and you need INFET simply because the battery will always have a path to SYS (otherwise you would back-drive your input supply from the battery) unless you can guarantee that VIN will always be greater than the battery voltage (say the adapter broke and supplied less than the battery - then the battery would back-drive it and potentially cause damage).

    Capacitors can be reduced based on your operation conditions. Run through the datasheet equations to determine how much cap you need. The demo board is over-sized to fit all configurations and output 8A. I'm not sure how much charge current you need.

    Regards,

    Zack

    PDF

  • Thank you for the detailed response, I appreciate it.

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