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UCC3750: UCC3750 CIRCUIT HELP

Gaurav bhargav
Prodigy 10 points
Part Number: UCC3750

In the datasheet we are using circuit as per application information provided in the datasheet, Now Q4(2N7001DICT),Q5(2N5457),Q6(MPSA06) ( KINDLY SEE ATTACHMENT ) of the reference circuit given got obsolete from the market.Kindly tell us if possible any alternate for these supportive components( Q4-Q6) so that our circuit will function without degrading of its quality .

  • 0
    TI__Mastermind 27885 points

    Hi Gaurav,

    TI does not cross reference or recommend equivalent alternate suppliers/PN's for discrete transistors. When searching through Octopart, I do see plenty of stock on MPSA06 at several distributors and there are functional equivalent recommendations that can be seen at Components101 here. TI has our own online IC cross reference tool here and discrete transistor suppliers may also have on-line cross reference tools on their websites?

    I will say the three transistors you mentioned are fairly benign in terms of their performance characteristics. There is nothing "high performance" about these devices so if you do need to find alternate PN's, look for functional equivalent gain, voltage, current and of course package.

    Thanks for connecting through E2E.

    Regards,

    Steve M

  • 0 in reply to Steven Mappus1
    Prodigy 10 points

    Dear Sir

    Can you describe what is the purpose of the circuit attached with this IC(UCC3750)?....without this portion of circuit means without Q4,Q5 and Q6 the ringer output is fine,but some times MOSFET across R22 and C22 get shorted ,even after satisfactory working for one month.Can you plz explain what this portion of the circuit do like is it some sort of surge protector or something like this?

  • 0 in reply to Gaurav bhargav
    TI__Mastermind 27885 points

    Guarav,

    Q4, Q5 form a cascoded switch to drive Q6 which is used to speed up the turn off of the gate drive (reduce switching loss in the main power MOSFET). Q4-6 are part of the gate drive circuit necessary to efficiently drive the main power MOSFET. You should consider to measure the VGS and VDS of the main power MOSFET with Q4-6 installed and removed and use these measurements to convince yourself of the importance. I believe if Q4-6 are not installed you will see additional switching loss on the main power MOSFET and this may be contributing to the failure you are seeing?

    Regards,

    Steve M