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Backup battery charger and power scheme design

Poh Leong Ng
Intellectual 745 points
Other Parts Discussed in Thread: BQ24075, TPS22929B, BQ24133, BQ24070, BQ24170, BQ24172, TPS61175, TPS54260, BQ24617

I have a design problem. The preliminary power tree of my system is shown below:

7217.Power Management Preliminary.pdf

 

My preliminary proposal for the power management scheme is shown below:

5340.Power Management Proposal.pdf

 

Is my proposal reasonable sound or there is a simpler method to get all the voltages? What is a good protection circuit or IC that I can used to prevent the usual automotive battery condition (cold crank, load dump, etc)?

Poh Leong

  • 0
    TI__Guru 56650 points

    For charger IC, bq24075 has a "SYSOFF" pin. MCU can monitor the battery voltage and control the "SYSOFF" pin. So, it can save a load switch IC.

    Your proposal is good to me.

    BYI, I can not find TPS63610 or TPS22929B on the website. Please consult "Power Interface" or "Linear Regulators" or "Non-isolated DC/DC" groups which are in charge of those ICs. They may have some suggestions.

  • 0
    TI__Intellectual 2295 points

    (1) The battery charger bq24070 and load switch TPS22929 can be replaced by a charger IC with power-patch management like bq24170, bq24172 or bq24133.

    (2) If they can use 12V car battery only. The TPS54260 + bq24070 + TPS22929 can replaced by a single charger IC as in (1) and then replace TPS63610 with TPS61175 (18Vin max).

    (3) If they must have 12V/24V car battery but they can use 2cell Li-po and a single charger like bq24617 (need external FETs) then replace the TPS63610 with a buck DC2DC like TPS54260.

  • 0 in reply to Bin Chen36084
    TI__Expert 8890 points

     

    Regarding the LDO selection: Your proposal is very good. Please be aware of the capacitance values that yield the desired AC performance for your application (as seen in the data sheet). And also be aware of the use of the feed-forward capacitor shown in conjunction with the TPS79501 (adjustable) on page 9 of the data sheet. 

  • 0 in reply to Bill Stokes
    Intellectual 745 points

    Hi All,

    Thank you for the suggestions. They are very useful.

    I have one more question. Regarding the protection circuit for load dump and cold cranking, is there a single IC solution? I also tried looking for app notes in the TI website on protection circuit for automotive using discretes but can't find anything useful. Could someone point me to the source if there is one?

    Poh Leong

  • 0 in reply to Poh Leong Ng
    TI__Guru 73830 points

    We do not have any devices designed specifically for load dump protection. We do have devices that are load sump tolerant due to their higher supply voltage ranges. We typically customers implement load dump protection using a MOV or similar device. I attached a slide with some options that have been seen.