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Original question:

BQ25756: How to Getting started.

BQ25756: Any hints on the design changes required to operate this part in forward mode only?

Ali Al-Sheikh
Prodigy 150 points
Part Number: BQ25756
Other Parts Discussed in Thread: BQ25820,

Tool/software:

I intend to design a boost-converting solar charger for a battery pack.

  1. To clear my doubts, am I correct in assuming that it can be designed to operate in forward mode only?
  2. What hints can you give me regarding the extra switching gates when I only need boost conversion in forward mode? I intend to remove all extra components for a cost-effective BOM

Cheers,

Ali Al-Sheikh

  • 0
    TI__Mastermind 31420 points

    Hello Ali,

    Thanks for working with us on this.

    1. Yes, the charger will work in forward mode by default.
    2. The charger will need all 4 switching FETs to operate. The 4 FETs don't need to be the same though. You can replace the buck side with cheaper FETs.

    Let me know if you have any more questions about this.

    Best Regards,
    Ethan Galloway

  • 0 in reply to Ethan Galloway
    Prodigy 150 points

    Thank you, Ethan.

    We do not need Buck operation. We have a low-voltage solar panel at the input and a higher-voltage battery pack that we need to charge. Can we just populate the bare minimum components to charge the pack? (We only need boost-conversion and in forward mode)

    Asking as it would be a huge PCB real estate and BOM cost if I were to populate all gates.

  • +1 in reply to Ali Al-Sheikh
    TI__Mastermind 31420 points

    Hello Ali,

    Thanks for being patient with this.

    Ali Al-Sheikh said:
    Can we just populate the bare minimum components to charge the pack?

    The charger will need all 4 switching FETs to function correctly. The charger uses all 4 FETs to detect the inductance.

    We do have a buck-only charger called the BQ25820, but we don't have a boost-only version of the BQ25756. We do have a boost-only charger called the BQ25883, but it doesn't support the same power levels of the BQ2575X family of parts

    Best Regards,
    Ethan Galloway