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UCC25800-Q1: UCC25800-Q1

PRATEEK SINGH
Prodigy 20 points
Part Number: UCC25800-Q1
Other Parts Discussed in Thread: UCC25800

Tool/software:

On page no.31 of the datasheet of UCC25800-Q1,  the value of parasitic capacitance at pin SW is mentioned as 170pF. Is this the parasitic output capacitance value across each of the two MOSFETs present inside the IC?? Or is it the combined total parasitic output capacitance of the two MOSFETs, thus implying that each MOSFET is having a parasitic output capacitance of 85pF??

  • 0
    TI__Mastermind 32825 points

    The output capacitance (Coss) of a MOSFET is non-linear with a strong VDS voltage dependency.  A few comments I can offer about the Coss:

    1. The 170pF you are referring to from the data sheet is the total capacitance at the SW pin. C_SW=170pF
    2. 170pF is estimated at VCC=15V (Table 9.1, page 29) but due to the non-linearity mentioned previously, the total SW pin capacitance is varying from about 180pF<C_SW<140pF over 12V<VCC<35V
    3. The HS/LS Coss contribution from each of the UCC25800 internal MOSFETs is not 50/50 but more like 60/40. For the 170pF (at VCC=15V), the Coss distribution is something like 100pF (HS) and 70pF (LS).

    Regards,

    Steve