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Original question:

BQ24780S: turbo boost mode and independent comparator

BQ24780S: Turbo boost mode battery discharge current

Bruce Lin_899
Intellectual 870 points
Part Number: BQ24780S

Hi Expert

My NB ODM customer have a adapter spec that need turbo boost work in100uS otherwise will trigger Adapter OCP.( adapter OCP 6A for more then 100uS )

We use 5A system power load rise in 5uS time for test.

We had done some test and modify the reg 0x37 Fast DPM Deglitch Time bits to 50uS, boost enable time will short then 150uS but still longer then 100uS.

And I measure the battery current found after boost work, current use around 80uS from little to start large current discharge.

I don't understand why IC need this time for discharge battery boost current. Is it normal or not? 

The picture channel 4 is battery current( scaler is wrong). Please help answer.

Thanks.

BR

Bruce 

  • 0
    TI__Expert 5330 points

    Hello Bruce,

    I am seeing similar timings, but in my capture, I see the IBATT first go to 0A in about 50 mS, then discharge about 1A for 100 mS, then discharge the full amount.

    Correspondingly, the IIN is going to 3A limit for this 100 mS for 1A discharge, whereas IIN_DPM is set to 2A in my example.

    I believe that this is due to the 2-level IIN_DPM.  I will try to verify this tomorrow.

    Regards,

    Steve

  • 0
    TI__Genius 16175 points

    Hi,

    I think your measurement result is ok for my understanding. I also attached one slide for your reference about our turbo-boost transient response.

    And maybe you should change deglitch time to 20us.

    Another solution maybe you should add more bulk cap to compensate load transient as well.

    Thanks

  • 0 in reply to Paul Yeh
    Intellectual 870 points
    Hello Steven

    Because the current probe and oscilloscope are different brand stuff, so the scaler is wrong. Maybe have 1A at that time.
    I had discuss with several man, we think desiner design several step for the boost voltage for safety thinking.
    Customer want to know the root cause of the current change time and want to know if it have any method can modify it on the circuit?

    Hello Paul

    Actually BQ24780S datasheet's minima value is 50uS , and the scope I post is 50uS setting!

    Thank you both for reply my question and with you have good day!
    Bruce
  • 0 in reply to Bruce Lin_899
    Intellectual 870 points

    Dear Sir

    Do we have any update?

    Customer want to know if there are any idea can improve less then 100uS?

    Thanks for feedback!

    BR

    Bruce

  • 0 in reply to Bruce Lin_899
    TI__Genius 10240 points
    Bruce,

    As you can find from the SW waveform in your measurement, the operation from buck transits to boost takes time. You can check to add caps on input side if faster response time is required to avoid the adaptor OCP.
  • 0 in reply to ezhao
    Intellectual 870 points

    Hi Eric

    Thank you so much!

    I will ask AA FAE continuous comucation with you .

    Thanks

    BR

    Bruce