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bq24650 / Vcc current (current into Vcc pin)

Ryuji
Guru 20090 points
Other Parts Discussed in Thread: BQ24650

Hello,

Please see the attached file as Vcc current which I measured by  EVM. 

6574.20141128_bq24650EVM VCC current.pdf

<Q1>
Vcc current is different between pre-charge and fast-charge.
Could you please let me know this reason ?

I think that the power loss equation is    "PICLOSS_Driver = VIN x Qg_total  x fs".

<Q2>
Vcc current has two peaks during 1 cycle.
Where in internal circuit of  bq24650 does bq24650 consume  these Vcc current ?

I think that the internal 6V LDO consume the 1st peak and level shifter consume the 2nd peak.  

<Q3>
Is Adapter supply current 25mA(typ) ,  mean of sum of current into Vcc pin?

Best Regards,
Ryuji Asaka

  • 0
    Guru 20090 points

    Hello,

    I'm looking forward to your reply.

    Best Regards,
    Ryuji Asaka

  • 0
    TI__Expert 5565 points

    <Q1>
    What is the difference that you are measuring between pre-charge and fast charge?

    There will be some difference between pre-charge and fast charge VCC current because the board (and the IC) heats up significantly (because of 10x higher charging current) more during fast charge, causing changes in Rdson and Cgs of the FETs. Also, at higher temperatures the operating current of the IC will tend to be higher (due to temperature variations in the IC such as oscillator frequency, reference currents, etc.).


    <Q2>
    Yes, it makes sense that the peak currents coincide with the high-side and the low-side switching. Since there is a bootstrap cap for the high-side gate drive, not all of the drive current will come from the VCC pin during turn-on of the high-side FET. This is why the 2nd peak is lower.

    <Q3>
    I believe that is a typo in the datasheet. The description should read "Adapter supply current (into VCC pin)".