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BQ25756EVM: MOSFET Selection of BQ25756

Mukunda M
Prodigy 30 points
Part Number: BQ25756EVM

Tool/software:

Hello,

We have used FDMS86350ET80 MOSFET in our board, But we are not able to turn on battery charging.
When we enable charge, the DRV_SUP get to 3.3 - 3.4V. Can you please check will our MOSFET work with the charger IC.
MOSFET used in EVK is "sir680ldp".

  • 0
    TI__Mastermind 20570 points

    Hi Mukunda,

    Are you testing on the BQ25756EVM board? If not, can you please share your schematic with us?

  • 0 in reply to Jing Zou
    Prodigy 30 points

    Hi Zou,
    Thanks for responding
    We are using BQ25756EVM board for our reference (As an EVK). We have only replaced the MOSFET's of that EVK with respect to our circuit. 
    MOSFET used in EVK is sir680ldp
    The MOSFET we replaced with that is  FDMS86350ET80

    Hope this helps you.

  • 0 in reply to Mukunda M
    TI__Mastermind 32681 points

    Hello Mukunda,

    Can you provide a register dump? I want to see if there is any answers in the register information.

    Can you provide your schematic, so I can confirm there is no issue?

    Best Regards,

    Christian.

  • 0 in reply to Christian Moyer
    Prodigy 30 points

    Hi christian,

    Everything in circuit is same as EVK, Only difference is the part number for mosfet is replaced from sir680ldp to FDMS86350ET80 and our inductor part number is 74439387100. We are now able to charge batteries and also able to increase and decrease charge current. 

    We are giving external DRV_SUP of 7-9V, because at 5V our MOSFETs were not turning on.

    Our maximum charge current is 1.6A.

    We are facing issue sometimes with our inductor heating up.

    Can you confirm us what can be the ideal value of external DRV_SUP and gate resistances for the MOSFET to solve inductor heating up issues.

    One more observation is that at external DRV_SUP 6.3V, inductor doesn't heat up. But sometimes at 6.3V, MOSFETS doesn't turn on because of lower Vgs.

    Thank you

  • 0 in reply to Mukunda M
    TI__Mastermind 31275 points

    Hello Mukanda,

    Thanks for being patient with this. We are pretty busy at the moment. I am looking into this and I will get back to you later this week.

    Best Regards,
    Ethan Galloway

  • 0 in reply to Ethan Galloway
    TI__Mastermind 31275 points

    Hello Murkanda,

    Once again, thanks for being patient here.

    Can you send us photo of what the SW1 and SW2 signals look like?

    Do HIDRV and LODRV look okay as well?

    Best Regards,
    Ethan Galloway