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BQ25710: BQ25710

user4819317
Prodigy 160 points
Part Number: BQ25710

Hi,

About BQ25710 datasheet description, what's the  purpose of the inductance detection through IADPT PIN?

  • 0
    TI__Genius 16185 points

    Hi,

    For BQ25710 control loop design, we need to sense input average current via Rac (input current sense resistor-10mohm). But during buck mode condition, BQ25710 only can sense half input current information during high-side FET is turn on. IC can't  sense the other half current information. So we need to let IC knows inductor value then can re-produce the other half input current information. And we use different IADP pin's resistor  value to inform BQ25710 "current inductor value". And this detection only did once when BQ25710 first power on whatever power source from AC adaptor or Battery.

    Thanks

     

  • 0 in reply to Paul Yeh
    Prodigy 160 points
    Hi Paul,
    Thanks for your quick reply, u can call me Eddy.
    I almost understand what you mean.
    What you said is: But during buck mode condition, BQ25710 only can sense half input current information during high-side FET is turn on. IC can't sense the other half current information. ---> How does BQ25710 judge into buck mode? How does BQ25710 operate seamless transition among buck,boost and buck-boost mode?
  • 0 in reply to Paul Yeh
    Prodigy 160 points

    Hi Paul,

    I have some questions need to ask you when I read the BQ25710 datasheet:

    1. About BQ25710, ChargeOption3 Register (addr=32H),  what's purpose to design IL_AVG clamp?  As I understand, peak and valley current limit is design, the average current limit not need to design.

    2. About BQ25710, Reg21[9], as I understand the bit is : before enable VAP function, should detect the battery strong enough or not via discharging 7 consecutive times on vbus? can you describe the bit function in detail? 

    3. What is purpose of the  LOW_PTM_RIPPLE bit ? can you describe the PTM control process?

  • 0 in reply to user4819317
    TI__Mastermind 25800 points
    Hello,

    1. The average current clamp is to prevent the inductor current from going so high so as not to destroy the external switching FETs this high inductor ripple. Granted, this is not exactly looking at peak inductor current, but a designer can consider this. This can also help prevent inductor saturation for designers looking to cost-optimize their inductor Isat value.

    2. In order to charge the input decoupling capacitors to 20V, the battery voltage needs to be at a minimum value to start the reverse boost mode to do this from a 1S or 2S battery. If the voltage is too low to enter boost mode to charge the caps or the current used to charge them is too high, then the VAP mode is not activated.

    3. LOW_PTM_RIPPLE bit is used to reduce the voltage/current ripple when in PTM mode. Because we are driving HSFET1 and HSFET2, there will need to be a charge refresh of each BTST capacitor for each FET. Doing this can cause a large delta across the inductor during PTM. This bit reduces that ripple during the BTST capacitor refresh.


    Regards,
    Joel H
  • 0 in reply to Joel Hernandez II
    Prodigy 160 points
    I have tested thre demo and understand it . appreciate your answer.