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TPS65910AA1RSL - with SITARA AM335x

Eric Mac
Intellectual 435 points
Other Parts Discussed in Thread: TPS65910

I am using the TPS65910A1 to power the Sitara AM335X.

What is the VBACKUP voltage limits (min, max) specifications for this IC?

Currently the design is using a Lithium Ion rechargeable battery connecting to the VBACKUP terminal of the TPS65910. This is used to support the RTC functionality. This series battery when fully charged is a 3.0 Voltage source. I am interested in switching to a higher capacity lithium battery having a nominal Voltage of 3.6V.

The nearest  parameter in the SWCS046N –MARCH 2010–REVISED APRIL 2012 datasheet for VBACKUP I can find is VRTC_LDO when in BACKUP, which is specified at 1.9V min and 3.0V max. I would find it difficult to believe this applies to VBACKIP since the max voltage of lithium ion battery as used on the reference design is at the limits without margin.

So, what is the VBACKUP Voltage range?

Thanks,

  • 0
    Intellectual 435 points

    This is the body of an email which I recieved from the Tech support Team at TI thru Arrow Electronics:

    Start of email

    --------------------------------------------------------------------------------------------------------------------------------------

    Certainly VBACKUP pin can handle 3.6v, it is not going to cause any issue to the device as if this pin it not used we recommend to connect it to VCC5.

    But the recommended backup battery charger range is 3.15v.

    ----------------------------------------------------------------------------------------------------------------------------------------

    end of email

    I have two designs using this PMIC.

    One design I am not using Vbackup to back up the RTC. The Vbat voltage is 5V and this voltage connect to all the PMIC VCC pins including VCC5. I still can not find the VBACKUP specifications for the voltage range of this pin. Since VBACKUP can be connected to VCC5 and VCC5 can be 5V, then VABCKUP can be 5V?

    The other design uses the internal RTC and I am selecting a battery that is not rchargable and outputs a nomial 3.6 V Voltage. To disable the charger is Register  BBCH_REG bit 0 the only setting I need to be concerned with?

    Thanks,

    Eric

     

  • 0 in reply to Eric Mac
    TI__Expert 6090 points

    VBCKUP spec is same as of VCC pins. It is recommended that if VBACKUP pin is not used connect is to VCC pins specifically VCC7 ( tolerance mentioned on page 7 of data sheet).  I agree its not very clear in datasheet.

    There is schematic checklist on ti.com product foder TPS65910 which describes the connection when pins are not used.

    http://www.ti.com/product/tps65910

    In the other design where you are using non -rechargable battery you do no have to do anything . By default backup battery charger is disabled. Just for description BBCH_REG is the register and bit {0} = BBCHEN , enables or disables the backup battery charger.

     

    Hope this helps ! Let us know if you have more questions.

  • 0 in reply to Eric Mac
    Intellectual 435 points

    I am aware of the checklist. My concern was since I am using 5V for VCC and not 3.3v as in the reference design and the data sheet was not clear on the VBACKUP limits. Your reply that VBACKUP has the same limits as VCC answers my question - thanks.