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BQ24725A: Data Sheet Figure 27 (Typical System Schematic for 5V Input 1S Battery

Patrick Chew
Prodigy 130 points
Part Number: BQ24725A
Other Parts Discussed in Thread: BQ25616, BQ25611D, , BQ40Z50-R2, BQ25883, BQ25886

Hi,

I come across the application circuit (Figure 27) in the datasheet where battery pack output isnt connected to charger and BATDRV is left open. I feel this architecture met my requirement where i want my battery to power up my entire system except the battery charger, this could probably improve my battery life. 

However i am wonder if voltage present to the PHASE, SRP and SRN pin is ok while the battery charger is powered off?  Will it incurs any problem?  I cant find more description on this architecture. 

  • 0
    TI__Genius 10240 points

    Hi Patrick,

    For 5V 1S application, could you check whether BQ25611D (host controlled charger) or BQ25616 (no host required) can meet your requirements? They are fully integrated chargers (all MOSFETs are integrated) and the design could be simplified. 

  • 0 in reply to ezhao
    Prodigy 130 points

    Hi Eric,

    My battery is a 2s2p battery (7.2V). That the reason why I am using BQ24725A. I have a fuel gauge (BQ40Z50-R2) communicate with this charger IC. 

    Honestly, I dont think Figure 27 limited to 1S 5V charging only. I think i probably support up to 4s cells with Figure 27 architecture, do you agree? 

  • 0 in reply to Patrick Chew
    TI__Genius 10240 points

    Hi Patrick,

    Fig 27 is for 5V input 1S application. BQ24725A is a charger with buck converter topology. The battery voltage has to be lower than the input voltage. It can't be used for 5V input to charge 2S battery application. You can check BQ25883/BQ25886 which are for 5V input voltage and 2S battery charging.

  • 0 in reply to ezhao
    Prodigy 130 points

    Hi Eric,

    My input is a 12V supply. So IC should have any problem.

    My only concern is - during battery discharged, and if the charger IC is not powered, charger IC's pin PHASE, SRP and SRN will not cause unnecessary problem to my circuit (is there any drawback with this architecture?). I cant find any description for this architecture. 

    For example, 
  • 0 in reply to Patrick Chew
    TI__Genius 10240 points

    Hi Patrick,

    The charger IC is designed to work in the battery only condition. There is no concern to the pins you mentioned affecting the battery discharging.