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BQ24610: BQ24610 Power Path Management In Removable Battery Pack Application

Gabriel Xu
Intellectual 2135 points
Part Number: BQ24610

Hi BCP Team

My customer is planning to use BQ24610 in a new project and I have several questions.

Customers using 5S removable battery pack in their system. I wondering to know:

  1. When battery pack is removed or absent, will the pair of back-to-back P-FET in the input side will turn on and provide power for system load? (Under power path configuration)
  2. If customer transfer to without power path/ DPM  configuration to cost down, can adapter provide power to system load when battery pack have been removed? (Base on my understanding the answer is not?) Without power path schematic is shown in the below picture:

  • 0
    TI__Mastermind 24075 points

    Hi Gabriel,

    1. When battery pack is removed, there is still voltage on the SRN pin as BQ24610 has battery absent detection feature. As long as input adapter is present and above max charge regulation voltage (VCC>SRN so it is NOT in SLEEP) then ACDRV FET will be driven and there is a direct conduction path to SYS for it to be powered
    2. Same concept as above.

  • 0 in reply to Kedar Manishankar
    TI__Intellectual 2135 points

    Hi Kedar

    When you mentioned "SRN" in the previous conversation do you want to mention "ACN"?

    Because when battery is removed, SRN won't see any voltage before Q1 FET turn on.

  • 0 in reply to Kedar Manishankar
    TI__Intellectual 2135 points

    Another thing I want to know is if we replace back to back OVP and reverse blocking FET with diodes, could we still active DPM function by adding sensing resistor between ACN and ACP? 

    The second things I want to know after we simplify the design by remove the BATFET (Power Path), we can't achieve termination anymore. Will such system structure making the battery life (or life cycle) become shorter?

  • 0 in reply to Gabriel Xu
    TI__Mastermind 24075 points

    Hi Gabriel,

    1.    I meant SRN. From previous description the ACFET is indeed driven when you have a valid input voltage and no battery. You can refer to the battery absent detection or also observe on the EVM, that there is indeed voltage on the SRN pin. The charger will sink and source current as shown in the flowchart, and if no battery is present, then the output capacitor will charge and discharge quickly indicating no battery present. 
      1. THere is some misconception here, so I would recommend using an EVM to observe the results.
    2. Yes you can reduce BOM count by removing ACFET and replacing with diode, and DPM will still be active as long as you have the sense resistor between ACN and ACP. Keep in mind increased power loss when using diode over reverse blocking FET
    3. No, BATFET has no relation to termination current in this direct power path topology. Termination current is sensed across the sense resistor between SRP and SRN.

  • 0 in reply to Kedar Manishankar
    TI__Intellectual 2135 points

    Kedar

    Customer also want to know the proper value for pre-charge current. The charge current is 1A now. 

    What's the normal percentage between charge current and pre-charge current? What side effect will come if we set a large pre-charge current?

  • 0 in reply to Gabriel Xu
    TI__Mastermind 24075 points

    Hi Gabriel,

       Usually 10% of fast charge current is used for precharge current. For many of our standalone parts that only have 1 pin to fix charge current, the precharge current is automatically set to 10%. You will have to check with the battery manufacturer to make sure that higher precharge current is acceptable.