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BQ24610: Design Verification

Karthik B
Expert 1300 points
Part Number: BQ24610

Hi,

I am planning to use BQ24610 battery charging IC for charging 7.4V , 10AH capacity battery , the battery should be charged completly in 4hrs keeping that in mind I have made the circuit. Please verify it and provide your valuable feedback.

I am little bit confused and not clear on the functions of BTST,PH,LODRV,HIDRV pins and why those N mosfests are used ? Can anyone explain  me the process what is happening over that part?

Regards,

Karthik

  • 0
    TI__Mastermind 24075 points
    Hello Karthik,
    N MOSFETs are used for this synchronous buck converter operation. HIDRV is the gate voltage used to drive the High Side FET(HSFET) of the buck converter, and LODRV is used to drive the LOW Side FET(LSFET) of the buck converter. Since N MOSFET needs a higher gate voltage than source voltage to drive it, a bootstrap circuit is used to provide HSFET driver's positive supply, and this is BTST. PH is the switching node and is at the junction of LSFET drain, HSFET source, and inductor.
  • 0 in reply to Kedar Manishankar
    Expert 1300 points

    Hi Manishankar,

    Thanks for your reply 

    There some more doubt regarding Precharge current. there is one formula in datasheet where we have Viset2 is required to calcuate precharge current.Here there are two unknown parameter so one parameter must be assumed , which factor should be assumed , Should I assume precharge current, Please suggest?

    When no adpator is connected  how the IC will get the VCC voltage because in datasheet its specified that ACDRV# pin is pulled to VCC pin and I am not able to make out any physical connection to VCC other than Adaptor input?

    And when ACDRV is high Q1 is OFF and now if I connect adaptor to it how switching will happen?

    kindly request you to reply ASAP.

    Regards,

    Karthik

  • 0 in reply to Karthik B
    TI__Mastermind 24075 points
    Hello Karthik,
    1. Equation 4 in section 9.3.4 gives the setting for Pre-charge current. Viset2 is set based on your resistor divider settings for R15 & R16 (user guide schematic). Viset2 will be the voltage division between Pull-up voltage and ground w.r.t your resistor setting. Rsr is the sense resistor connected between SRP and SRN (recommended 10mΩ). No factor needs to be assumed, as the user has the ability to configure these values according to their application.

    2. When no adapter is connected VCC will be low, and as VCC<SRN (if battery is connected) then ACDRV is pulled to VCC. ACFET is a PFET which means gate voltage is negative w.r.t source voltage to turn it on. In this case gate and source voltage will be equal to VCC keeping PFET off, which will prevent reverse battery discharge. The key here is not the actual voltage on VCC, but Gate voltage of ACFET w.r.t Source voltage of ACFET.

    3. When adapter is plugged in and VCC is present, device comes out of sleep mode (if VCC>SRN) and after 30ms delay, ACDRV is set to VCC-6V by internal regulator to turn ACFET on, connecting adapter to system and switching can occur.