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bq24261/2

Perico Eldelospalotes
Intellectual 505 points

Hi!

I have doubts about this charger:

1.- In the datasheet states that when in DEFAULT mode, with the PSEL pin we can choose between WALL ADAPTER or USB. When LOW, the WALL ADAPTER mode is selected. So, when high or floating, USB mode is selected?

2.- But, if an I2C write is done, PSEL pin will be ignored. So if we are using a WALL ADAPTER, do a I2C write and then we connect an USB, how we can change the charging current? Only via I2C?

3.- Imagine we have this scenario: We want to power the entire system and charge the battery from an USB. The current of the USB port is only 100 mA (imagine that no enumeration has been done and, subsequently, 100 mA is the maximum current). The minimum charge current that the bq24261/2 allows is 100 mA, so how we can power the system and charge the battery?

4.- Appart from the default USB current when PSEL is selecting USB as the input power source (100 mA in the bq24261 and 500 mA in the bq24262), is there any other difference between these two chargers?

            Thank you in advance.

  • 0
    TI__Guru**** 167196 points
    Regarding 1, Drive PSEL high to select USB100 (bq24261) or USB500 (bq24262) mode, drive PSEL low to select
    1.5 A mode. PSEL cannot be left floating.
    Regarding 2, the first I2C write puts the IC into HOST mode and will change the input current limit to the default value of 1A. PSEL is only active in standalone mode.
    Regarding 3, if the system requires more power than 100 mA input current can provide, the charger will stop charging and enter supplement mode to power the system from both the battery and the 100mA input current limited buck converter.
    Regarding 4, bq24262 has default (standalone) mode VBATREG=4.2V, charge enabled in default mode and no watchdog or safety timers. bq24261 has default (standalone) mode VBATREG=3.6V, charge disabled in default mode and watchdog or safety timers are active.