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TPS65930: Backup battery question

mbardinica
Prodigy 20 points
Other Parts Discussed in Thread: TPS65930, TPS65950, OMAP3530

I have a customer that wants to use TPS65930 to power supply OMAP for a video phone application (volumes are 5kpz/yr)

Customer wants power supply TPS65930 at 3.3V but have some doubt:

He wants to use a backup battery for RTC connected at BKBAT pin (pad H9). At page 45 of datasheet (SWCS037D.pdf) was written that the condition for this backup battery are 2:

1)       Main battery voltage > backup battery voltage

2)       Main Battery > 3.2V

Can be a risk to have only 100mV margin respect 3.2V minimum requested for the charger? (The 3.3V is regulated and stable)

Furthermore the battery charge voltage is selectable with 4 different value (2.5V 3.0V 3.1V 3.2V) as descript at pg 293 of SWCU052C.pdf.

The limit specified at point 2 above (main battery >3.2V) remains 3.2V or follows the battery charge voltage (i.e. is 2.6V for battery charge set to 2.5V)?

  • 0
    TI__Genius 15100 points

    Hi,

    The TRM is missing some information for backup battery. You can refer to the TRM section for TPS65950 for backup battery. I am in the process of correcting the TRM and will make the changes. The four voltages you specified are for end-of-charge for the backup battery. For backup battery to charge the main battery has to be greater than 3.2V. Backup battery is used for providing supply to RTC section/module only when the main battery is not able to supply the backup domain. This happens only in backup mode and some conditions of main battery supply. Also, the backup battery charge will be in uA. You can refer to sections 7.4.2.1, 7.4.2.2 and 7.4.2.3 in the TPS65950 TRM.

    I hope this is clear. Let me know if there are more questions. Please put your question on forum, I will reply the same on the forum.

     

    Regards,

    Gandhar

  • 0 in reply to Gandhar Dighe
    Intellectual 390 points

    Hi,

    We are designing the board with OMAP3530 cus package and TPS65930PMIC Chip.

    Since Vin voltage range of PMIC is 2.7 to 4.5V. I am giving 3.3V input to the PMIC chip.

    When i am selecting 3.3V input for PMIC, should i consider any other points?

    Is there any issues? Please help me. I am going to release my gerber by this weekend. So calrify this. I am also supporting RTC battery for backup.

    Regards,

    Murugan.M

  • 0 in reply to Murugan Mayileri
    TI__Genius 15100 points

    Please refer the following post, it will be helpful:

    http://e2e.ti.com/forums/p/11073/43115.aspx#43115