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CSD17483F4: leakage current question

Patrick Chen(TPE System & Application)
Expert 3430 points
Part Number: CSD17483F4

Hi Sir,

My customer is using the CSD17483F4 as an level shifter function for an OSC(32687HZ)

There is a mode that the system do not have power and only a back up battery supply power to the OSC.

And at this mode CSD17483F4 did not have any power apply on it, but there is a 2.5V square wave input to Gate pin of CSD17483F4 and customer will see a 24uA total power consumption, but if they change to a similar spec mosfet, the total power consumption will be down to 8 uA.

May I have your help to advise why CSD17483F4 have a higher leakage current?

the attachment is how they connect CSD17483F4.

Many thanks

Patrick

  • 0
    TI__Mastermind 29525 points

    Hi Patrick,

    Thanks for the question. The current your customer is measuring is not due to IGSS which is specified as 50nA max at VGS = 10V & VDS = 0V in the datasheet. Even though the drain-source voltage = 0V, charge is being transferred into and out of the input capacitance of the FET as it is being charged and discharged between 2.5V and 0V every cycle. From the Gate Charge vs. VGS plot shown in Figure 4 of the datasheet, QG = 0.6nC at VGS = 2.5V. The average gate current is then dQG/dt = 0.6nC x 32687Hz = 19.6uA (0.6nC is typical and there is some variation from part-to-part and lot-to-lot). When the customer tries another FET and they measure lower current, that FET must have lower gate charge at VGS = 2.5V. Do you have the part number for the other FET or know what its gate charge is at VGS = 2.5V?

  • 0 in reply to John Wallace1
    TI__Mastermind 29525 points

    Hi Patrick,

    I'm assuming my previous reply answered your question. I am going to close out this thread. Please feel free to contact me if you have any additional questions.