• State TI Thinks Resolved
  • Locked Locked
  • Replies 4 replies
  • Answers 2 answers
  • Subscribers 65 subscribers
  • Views 416 views
  • Users 0 members are here
Support feedback
Options
Options
Similar topics

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

BQ25890: Current limit of BQ25890 and default current limit of the BQ25890 IC without D+/D- line detection

yagnik pokal
Prodigy 20 points
Part Number: BQ25890
Other Parts Discussed in Thread: BQ24253

I am plan to use BQ25890 IC in my design. 

I needed a few answers.

1) BQ25890 supports 5Amp hence I needed 3 Amp on SYS voltage(Power path) and 2 Amp on battery charging. does it is possible?

I don't want to connect D+/D+ lines since my charger doesn't have these pins. My charger is able to give 5V @3.2Amp.  I want to know that is there any possibility that the input current is limited and I don't get 3Amp on the power path SYS line and 2Amp on a battery charge?

2) What is by default the current limit if we do not use any I2C configuration and D+/D- line detection for battery charger and power path management? I know it is written in table no 6. But apart from that table anything which will limit the input current? 

  • 0
    TI__Mastermind 19100 points

    Hi Yagnik,

    1) 3A SYS load and 2A battery charging is possible with the BQ25890. However, for such an application I would recommend 9V or 12V at VBUS.

    If we assume a minimum VSYS target voltage of 3.5V (VBAT sitting slightly below this voltage across the BATFET during Fast Charging) and we have a 5A buck output target with both the SYS load and charging load combined, that's already 17.5W of power needed from the buck regulator. A 5V adapter at 3.2A is only going to input 16W of power in an ideal case, so you would need something more powerful at the input (even after ignoring efficiency considerations) to make sure the adapter isn't overloaded.

    To ensure that there is no extra current limiting, you will need to either connect the ILIM pin to GND, or disable the ILIM pin functionality by setting REG00[6] = 0b (default is 1b). You may also want to short the D+/D- pins together so that the device automatically detects "DCP" during the input detection stage and sets the digital current limit (IINLIM) to 3.25A. You can change the IINLIM setting via I2C otherwise.

    2) If the D+/D- lines are left floating, the device will detect an "Unknown Adapter" and the input current limit (IINLIM) will be set to 500mA. If the D+/D- pins are shorted together, the device will detect a "DCP" connection and the input current limit will be set to 3.25A.

    Note that the actual input current limit will the the lower value between the IINLIM setting and the ILIM pin setting. 

    Regards,

    James

  • 0 in reply to James Steenbock
    Prodigy 20 points

    One more question is that if I connect D+/D- lines as mentioned in point no 2. The USB cable of my charger doesn't have D+/D- wires. And it is only having the +5V and ground.

    So still it will enter into DCP mode or not?

    If not is there any I2C settings or default configuration where it limits the current 3.25A?

    I am asking this because we already have an issue with the current limit and power path management with BQ24253. I don't want to repeat that in the second revision.

  • 0 in reply to yagnik pokal
    TI__Guru 52091 points

    Hi,

    Because of the holidays, we will get back to you after Jan. 3, 2023.

    Thank you for your patience,

    Ning

  • 0 in reply to yagnik pokal
    TI__Mastermind 19100 points

    Hi Yagnik,

    If you want the device to enter DCP mode automatically, the D+/D- lines should be shorted together. If your USB cable does not have D+/D- connections, you will need to find out what the D+/D- pins are seeing when you connect the adapter. The D+/D- pins will check for an input regardless of your USB connection unless you disable auto input detection by setting REG02[0] = 0b.

    The BQ25890 does not limit current to 3.25A by default unless DCP is detected during auto input detection. When the detection is disabled, the IINLIM register keeps its previous value.

    For more information see Section 9.2.3.3 of the datasheet.

    Regards,

    James