• State TI Thinks Resolved
  • Locked Locked
  • Replies 4 replies
  • Answers 1 answer
  • Subscribers 63 subscribers
  • Views 578 views
  • Users 0 members are here
Support feedback
Options
Options
Related

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.

Linux/BQ24296: How can i supply 4.2V to VSYS with disabled charging?

Dongil Park
Prodigy 30 points
Part Number: BQ24296

Tool/software: Linux

Hi.

I'm using bq24296 charger just for the regulation to VSYS without battery.

I want to supply 4.2V to VSYS but it has dropped to 3.65V when i disable charging.

I want to disable charging because i don't have a battery.

Can i supply 4.2V to VSYS with disabled charging? Could you please help me to enabling this?

Charger

 BATFET 

 VSYS

 Enable

 Enable

 4.2V

 Disable

 3.65V

 Disable

 Enable

 3.65V

 Disable

 3.65V
  • 0
    TI__Mastermind 25800 points

    Hey Dongil,

    I have a few comments and questions:

    1) Will you ever use a battery in this system? If not, what features of the charger are you utilizing for your application that keep you from using a standard buck converter? At it's core, the charger is just a buck converter with a Li-ion IV profile.

    2) SYS can only operate at the VSYSMIN threshold without a battery AND charging disabled. This is inherently the function of the NVDC architecture of many chargers. Vsys is only 4.2V when charging because the BAT pin is being moved between the VBATREG threshold and the Recharge threshold. As soon as the BATFET is disabled without a battery, SYS will drop to the VSYSMIN threshold. If you like to maintain VSYS @ 4.2V, I suggest keeping Charge Enabled and the BATFET on. There will be minimal current flowing into the BAT anyway, as it will reach the termination threshold very quickly. 

    Regards,

    Joel H

  • 0 in reply to Joel Hernandez II
    Prodigy 30 points
    Dear Joel H,

    Sorry for late response.

    1. We have change the device specification which doesn't support charging feature because we didn't verify the functionalities.
    But Our device has a battery connecter so that user can attach battery, so we decide to use it as a buck converter and disable charging.

    If we enable charging at a minimum charging current without battery, can we supply 4.2V to VSYS?
    I think even we enable the charging, minimum charging current can avoid some other issues from battery user.

    How's your opinion? Is it possible to set a minimum charging current like a pre-charge current?
    I'm sorry that asking about abnormal use cases.

    Thank you.

    BR.
    Dongil
  • 0 in reply to Dongil Park
    Prodigy 30 points
    Dear Joel H,

    When i test with charging current 512mA, VSYS is 4.2 during CHRG_STAT changed from Fast Charging to Charge termination.
    Does it means VSYS is regulated with 4.2V even charging has done?

    Could you please let me know this behavoir?

    Thank you.

    BR.
    Dongil
  • 0 in reply to Dongil Park
    TI__Mastermind 25800 points
    Hey Dongil,

    If the user connects the battery, will you ever attempt to charge it? Is it possible, even the battery connector, to electrically disconnect the battery from your design?

    In regards to enabling charge with minimum charging current, you can supply 4.2V to VSYS, but it will also fall to ~4.0V at times. It will not remain regulated for too long. Also, pulling current from SYS after termination has completed will likely pull SYS to VSYSMIN at times.

    In regards to pre-charge current, or low current, this part has a minimum of 512mA. Pre-charge current levels only exist when the battery is below the VBATLOW threshold.

    In regards to your last post, VSYS will remain up at VBAT+150mV until the BAT node begins to droop, after charge terminates. The BAT droop will be much faster when a load is applied.


    Regards,
    Joel H