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BQ25601: Part solution needed for application with Li-Ion Battery

Daniel Brown
Intellectual 870 points
Part Number:

I need some help find a part solution for my application which is the following:

Computer chipset: Sitara AM3351 with DDR and eMMC:
Currently using TPS65217C to provide regulated voltages

Board VIN = 5V

I am adding a Li-Ion battery to the system and need a way to charge it and manage it (hopefully, using
the TPS65217C already design in). However, I discovered I will need Icharge = 2A or more.

Vbat-max = 4.2V
Vbat-min = 3V

So, I thought I might add the BQ25601 to charge the battery and manage the powerpath. However, I planned
to take the Vsys of the BQ25601 and tie it to VAC of the TPS65217C. And this will work, I think, because the
regulated Vsys voltage around 3.65V of the BQ25601 is below the turn on voltage of the VAC input. 

Should I change the way I think about using these parts? Should I use a different battery charge chip? Should
I use a different PMIC?

  • 0
    Intellectual 870 points

    Daniel Brown said:

    Part Number: BQ25601

    I need some help find a part solution for my application which is the following:

    Computer chipset: Sitara AM3351 with DDR and eMMC:
    Currently using TPS65217C to provide regulated voltages

    Board VIN = 5V

    I am adding a Li-Ion battery to the system and need a way to charge it and manage it (hopefully, using
    the TPS65217C already design in). However, I discovered I will need Icharge = 2A or more.

    Vbat-max = 4.2V
    Vbat-min = 3V

    So, I thought I might add the BQ25601 to charge the battery and manage the powerpath. However, I planned
    to take the Vsys of the BQ25601 and tie it to VAC of the TPS65217C. And this will work, I think, because the
    regulated Vsys voltage around 3.65V of the BQ25601 is below the turn on voltage of the VAC input. 

    Should I change the way I think about using these parts? Should I use a different battery charge chip? Should
    I use a different PMIC?

    Sorry, what I meant to say above is that "And this will NOT work, I think, because the
    regulated Vsys voltage around 3.65V of the BQ25601 is below the turn on voltage of the VAC input."

  • 0 in reply to Daniel Brown
    TI__Mastermind 25800 points

    Hey Daniel,

    You are correct as this will likely not work. The PMIC will likely show some strange behavior outside of its recommended operating range. 

    One question is whether you will always have an adapter present at VBUS/VAC? If so, consider using the bq25601, but use the same input to power both the charger and the PMIC. 

    I would also reach out to our PMIC team here. They may be able to find you another suitable PMIC that has the same sequencing requirements for the AM3351 and give 2A of charge current. 

  • 0 in reply to Joel Hernandez II
    Intellectual 870 points
    No, the the VIN = 5V (adapter) will NOT always be present, I need the OR'd combination of VIN and BAT to power a PMIC input.

    I was looking at other PMICs that were designed for the Sitara series. The TPS650250 looked good for the low input voltage operation but it
    does not have built in sequencing. The TPS65218 looks similar to the TPS65217 and does seem to have the low input voltage operation and sequencing. Might the TPS65218 be a possible PMIC replacement?
  • 0 in reply to Daniel Brown
    TI__Mastermind 25800 points
    In terms of input operating voltage, the TPS65218 seems sufficient.

    In terms of power sequencing for your processor, I would post to the PMIC e2e forum to verify if there are any compatibility issues.

    Another comment is based on the operating voltages required by your processor. While it may be the case that the PMIC can operate down to 2.7V of input, perhaps this lower input voltage does not guarantee the necessary regulated voltage rails required by your processor. However, again, I would recommend asking that team as they are more familiar with the part than I.


    Regards,
    Joel H
  • 0 in reply to Joel Hernandez II
    Intellectual 870 points
    Thanks. Yes, I agree that based that at VIN = 2.7V the regulators cannot regulate the required voltages for the processor or system, the highest of which is 3.3V. However, all I need is a turn on and continous operation that can do so below the Vsys of the BQ25601 of 3.65V or whatever my lowest Li-Ion batttery voltage happens to be. And this chip seems to qualify, along with other requirement necessary for the Sitara. I will contact the PMIC folks. Thanks.