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TIDA-00792: Alternate part for CSD13381F4 cell balancing MOSFET

Part Number: TIDA-00792
Other Parts Discussed in Thread: CSD13381F4, , BQ76940EVM, TIDA-00255

Hi TI Engineer,

I am referring to TIDA-00792 hardware design files and found that CSD13381F4 FemtoFETs are (used for cell balancing) available only with LGA package, it's difficult for mounting and troubleshooting. 

Can i use SOT563 package MOSFETs (FDY1002PZ, similar in bq76940EVM) with little changes with related resistors, diodes and capacitors?

Suggest a suitable MOSFET having SOT package along with minimum required changes. Balance current requirement is same 100 mA. 



  • Hi Vatsal,

    The TI FETs tend to be high performance devices in small packages which can be more difficult to work with as you indicate.   One of the requirements of TIDA-00792 was to use N-channel balancing FETs as an alternative to to the P-channel used on the EVM/TIDA-00255 for the advantages described in bq769x0 Family Top 10 Design Considerations.  You can certainly pick a FET from your favorite manufacturer or distributor, most will have search tools available.  Select a FET with a VDS rating to handle any transient on the cells, 20V may be a good value.  You want a FET with a defined RDSON at or below half the cell voltage you will balance.  So if you will balance at 4V you want a defined RDSON at 2V or less VGS.  Select a package which will handle the power for your design and is suitable to work with.  VGS maximum will typically be low for these type of FETs, so be sure the zener diode you use with the FET will protect its gate in the conditions described in the apnote while allowing normal operation.  

    While we would prefer you use a TI FET, you have options in the industry, but you must make the selection suitable for your design.

  • Hi WM,

    Thank you for reply.

    I will surely take your inputs with alternate MOSFET part.