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BQ24073 Input current dynamically

Jay Carlo De Claro
Prodigy 160 points
Other Parts Discussed in Thread: BQ24073, BQ24250, BQ24072, BQ24392

Hi Guys,

Currently I'm using BQ24073 IC for my battery charging, I fixed it to USB500, however, I'm thinking if this is possible to set dynamically (input current) from setting this to USB500 to 1A depends on the charger capability.

I want to set them from USB500 to 1A input current using a Power supply charger dynamically. First test if it is connected to USB.

The problem is that it should sense if it is connected to USB or is it just a power supply. 

Im open also to change my design if there is a better IC out there.

Your advise is highly appreciated or if you experience same challenge before.

Thanks and regards,

Jay

  • 0 in reply to Jeff F
    Prodigy 160 points

    Hi Jeff,

    What if I set the Ilim of BQ24072 to 1.2A? The reason is I want to get the maximum current to the port whether its 100mA then I will draw 100mA, if 500mA I will draw 500mA etc etc.

    What will happened to the USB port if I plug in the USB to a USB100 which can draw 100mA? Will I damage the port?

    It says that the  "Charging Control Topology is Linear", from my understanding it will automatically adjust the current according to the voltage, Am I correct? If not please help to ellaborate.

    By using this topology, Can I apply for USB2.0 compliance or higher? 

    Thanks and regards,

    Jay

  • 0 in reply to Jay Carlo De Claro
    TI__Guru**** 166986 points

    The charger is a "linear" charger meaning it based on a linear regulator and not a buck switching regulator.  If you set the current limit to 1.2A and the USB port cannot provide that much current, the USB rail will get pulled down to the bq24072/3's UVLO voltage (just below 4.0V), the charger will shut down and the USB  rail will recover.   The cycle will repeat, causing a square or saw tooth waveform from the USB rail.  You could add a bq24392 which performs primary and secondary detection on the USB port (compliant with the UBS Battery Charging 1.2 spec) and gives digit outputs report the USB port's capability and change the bq24072/3 ENx pins accordingly.  Alternatively, if you select one of the two USB options with EN2=0 (100mA or 500mA current limit), the bq24072/3's VINDPM feature is turned on and it will monitor the IN voltage and automatically scale back the input current limit to prevent the USB rail from collapsing.

    The bq24250 integrated D+/D- feature performs the primary and secondary detection and will automatically size the input current limit to match the USB rail at start up AND its VINDPM feature is on all the time.  After USB enumeration, if you can  increase the charger's input current limit if you so choose.