• State Resolved
  • Locked Locked
  • Replies 3 replies
  • Subscribers 63 subscribers
  • Views 364 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.

BQ25896: Output power for System from Power path management or Battery Supply?

Florian Mayerle1
Prodigy 40 points
Part Number: BQ25896

Hi,

I have a question about the output power from this device, because I find controversy information in the data sheet.

Under point 8.5 Electrical Characteristics it says: Vsys(min) = 3.5 to 3.65V
Under point 9.4.4 REG03 it says: SYS_min =3.0 to 3.7V
Symplified Schematic page one: SYS = 3.5 to 4.5 V

So which value does count for me?
Can I set the SYS_out to a fix value (3.5V max) ?

I want to use the Charger in combination with a LI-ion battery (2.8 -4.2V). My System operates on 2.3 - 3.6V and drains max 100mA.


Do I need an additional step down converter, like the TPS6273, to opperate this system?

If no:
There must be a fix output in all operation modes of BQ25896 for 3.0V to 3.5V.

If Yes:

Is it possible to use the BQ25896 while 5-14V power adapter is connected, to charge the battery and use the BQ25896 power path management in combination with the TPS6273 step down converter to power the System. And when no power adapter is connected only use the TPS6273 to transform the battery voltage directly from 3.1-4.2V to 3.0V output to power the system directly. I want to do this to increase the efficiency of light load power supply by using on step down converter to power the system instead of the power path management and step down converter in a row.

I look forward to hearing from you.

Greetings
Florian Mayerle

  • 0
    TI__Guru**** 166786 points

    Hi Florian,

    The MINSYS range is user selectable from 3.0V - 3.7V.  This is the voltage at SYS while the battery is below that voltage.  Once the battery rises above that voltage, SYS essentially follows the battery up to VBATREG + a few millivolts.  If your system max is 3.6V and your battery charges to 4.2V, you will need a buck converter following SYS.

    Regards,

    Jeff  

  • 0 in reply to Jeff F
    Prodigy 40 points

    Hi Jeff,

    thanks for your help.

    I`m still a bit confused, what is the register to set SYS-Voltage to absolute fixed value and what is its range.

    Greetings

    Florian Mayerle

  • 0 in reply to Florian Mayerle1
    TI__Guru**** 166786 points

    Hi Florian,

    There is no fixed SYS voltage as it follows the battery up as it charges.  You can only set the MINSYS when the battery is below V(MINSYS).

    V(BAT)>VSYS(MIN) - charge disabled - V(SYS)=V(BAT)+50mV typical

    V(BAT)<VSYS(MIN) - charge disabled - V(SYS)=V(SYSMIN)+150mV typical

    V(BAT)>VSYS(MIN) - charge enabled - V(SYS)=V(BAT)+70mV max

    V(BAT)<VSYS(MIN) - charge enabled - V(SYS)=V(SYSMIN)+150mV typical

    Regards,

    Jeff