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BQ24195: Charging without USB host

Aleksandr Sakharov
Prodigy 30 points
Part Number: BQ24195

Hello.

Is it possible to charge with current higher than 10mA using BQ24195 when D+ and D- pins floating in the air?
If I connect them to each other - chargeing starts normally with 1.5A, but when they floating in the air - only 10mA available (or even lower).
In spite of D+ and D- state, before charging starts in both cases values read from all I2C regs are same (REG08 bits VBUS_STAT always 0 and current settings set up to 1.5A).
But after charging starts, BQ24195 with shorted D+ and D- keeps charging with same values in I2C registers and high current.
BQ24195 with floating D+ and D- after start of charging chages valus of bits CHRG_STAT to 2 or 3 in cycle (Fast Charging/ChargeTermination Done). Probably, because current is too small.
Also, when D+ short with D- then REG08 don't show charging process, CHRG_STAT keeps 00 (Not Charging).


So, my question is how to launch charging when D+ and D- floating in the air? Is it possible?

Registers value in different states
BQ24195 D+ short with D-, charging  D+ short with D-, idle D+ and D- floating, charging D+ and D- floating, idle
REG00 30 30 30 30
REG01 1B 1B 1B 1B
REG02 60 60 60 60
REG03 11 11 11 11
REG04 B2 B2 B2 B2
REG05 9A 9A 9A 9A
REG06 03 03 03 03
REG07 4B 4B 4B 4B
REG08 05 05 24/34/25 05
REG09 00 00 00 00
REG0A 23 23 23 23
  • 0
    TI__Mastermind 25800 points
    Hey Aleksandr,

    It is possible to charge with the D+/D- lines floating, but please refer to Table 2 and section 8.3.1.3.5 HIZ State wth 100mA USB Host which describes the effect of leaving D+/D- floating. Effectively, the charger detects as a 100mA Host, and if the battery voltage is about the VBATGD threshold (~3.6V), then the charger will stop charging and go into HIZ mode.

    If you want to leave D+/D- floating, you will need to reprogram the input current limit to a higher value than 100mA.

    What I do not understand about your register dump is how when D+/D- is shorted, the input current limit detected is still 100mA. Is this not correct. Are you shorted the D+/D- lines before or after you apply VBUS?


    Regards,
    Joel H