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BQ24230: BQ24230 Operating over Vin and Vbat range

ANDREW SAUTER
Intellectual 270 points
Part Number: BQ24230

Can we get some input on the expected operation of BQ24230, we are a little confused by the datasheet?

The part is already a consumer device presently in DFM but we are new to the team.

Thanks in advance!

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USE-CASE #1 (TWO BATTERIES)

Vin =4.2V

Vbat = 4.0V

Questions: Will Vin begin to charge Vbat WHILE the Vout is connected to Vbat (i.e. Vout = 4.0V)

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USE-CASE #2 (DEEP DISCHARGE)

Vin = 4.2V

Vbat = 0V (Open circuit protection tripped)

Will the Vbat receive conditioning current charge WHILE Vout is regulated to 4.4V?  (provided: total Iin < 500mA)

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USE-CASE #3 (CHARGER PRESENT)

Vin = 5.0V

Vbat = 4.0V (Open circuit protection tripped)

Will the Vbat receive charge and WHILE the Vout is regulated at 4.4V? May the load draw 1.5A total?

  • 0
    TI__Mastermind 21590 points

    Hello Andrew,

    Case #1: You don't want to short VBAT and VOUT as this will bypass a lot of the internal circuitry. Out and VBAT are regulated to do different things. You'll pretty much have Constant Voltage on your battery which could damage it.

    Case #2: VOUT wont be regulated to 4.4V because VIN is below 4.4V. If the battery was present, you wont charge because VIN is below Vin-DPM ( 4.5V).  When the battery is absent, the battery detection routine is run as explained below. IBAT(det) is 7.5mA.

    Case #3: VBAT detection will be run and 7.5mA will be used to close the open circuit. If the load draws 1.5A, the battery will supplement with 1A since the maximum input current is 0.5A. This is explained in section 8.3.3.1.3 of the datasheet.

    Regards,

    Raheem

  • 0 in reply to Raheem
    Intellectual 270 points
    Case #1 (clarification)
    Definately we do not want to short Vbat to Vout (or Vin)! Will Vout source current from Vin? When Vin = 4.2V and Vbat = 4.0V.

    Case #2 (clarification)
    My mistype, I realize the Vout cannot be higher than Vin or Vbat! Will Vout be Vin - Vdp i.e. 4.0V AND while sourcing Vbat conditioning current? Let us assume here that total current is < 500mA, and if it exceed 500mA, I presume it will brown out.
  • 0 in reply to ANDREW SAUTER
    TI__Mastermind 21590 points
    Hello,
    Case 1: This device has a Vin-DPM voltage of 4.5V so the input current will be reduced. If your input voltage is 4.2V which is below the Vin-DPM voltage, the input FET will be off and the output will be powered by the battery.
    Case 2: If VIN is 4.2V, there wont be any current to close the open circuit protection because the infet FET is off due to VIn being below VIN-DPM.

    Regards,
    Raheem
  • 0 in reply to Raheem
    Intellectual 270 points

    I see that VIN-DPM is 4.5V, after which Iin is reduced!

    Do you have an equation for the reduction in current?

    Also p. 19 is illustrative.

  • 0 in reply to ANDREW SAUTER
    TI__Mastermind 21590 points
    Andrew,
    I don't have an equation for the reduction in current but i've seen that below 4.3V, there is no input current during my bench tests.

    Regards,
    Raheem