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BQ24171: Typical Application Schematic With Single-Cell Unremovable Battery

Kevin Carlborg
Prodigy 20 points
Part Number: BQ24171

Figure 23 in the datasheet shows an example where the battery is directly connected to the system. It explains that it is for 1-cell applications. The benefit is that the battery can automatically supplement the system load if the adapter is overloaded.

My question is if you can use this same configuration for a 3-cell application as well. Being able to supplement from the battery during high system loading is important to the design. If it is possible, is there anything that needs to change in Figure 23 besides the ISET, OVPSET, and FB pins? And what is the recommended value for the resistor between VREF and ACSET?

Thanks,

Kevin

  • 0
    TI__Guru 57701 points
    Yes, you may. The resistor between VREF and ACSET can be 100kohm. Thanks!
    Please click "This Resolved my issue" button if this post answer your question.
  • 0 in reply to Ning T
    Prodigy 20 points
    Hi Ning, Thanks for the quick response. I just have a couple more questions.
    I noticed that there is an integrated diode between the REGN and BTST pins. What do you gain by adding the optional D1 schottky shown in figure 23?
    In the figure 19 configuration, there is a schottky from the SW pin to PGND. I believe it's there to increase efficiency. Is it really not needed in the figure 23 configuration or can I add anyway?

    Thanks,
    Kevin
  • 0 in reply to Kevin Carlborg
    TI__Guru 57701 points
    Kelvin,

    D1: The integrated BTST diode has 0.85V typical voltage drop. Using optional external Schottky diode will improve the efficiency.
    The Schottky diode from SW to PGND: It is a must if the charge current is equal or greater than 2A.

    Thanks,

    Ning.
    Please click "This Resolved my issue" button if this post answer your question.