• State
  • Locked Locked
  • Replies 3 replies
  • Subscribers 63 subscribers
  • Views 1082 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.

TPS27081 with series connected LiPo

Mark McCormack
Prodigy 60 points
Other Parts Discussed in Thread: TPS27081A

Hi, I am controlling a 200ma motor with a microcontroller powered by a series connected 2-cell LiPo pack. For charging my plan is to use a single cell USB charger. To do this I need to switch the load out of the circuit and reconfigure the lipo's into a parallel configuration during charge mode.

The TPS27801 as well as the TPS208x chips have an 8V maximum rating. I am concerned that the  series connected LiPo pack can be as high as 8.4V when fully charged and unloaded. Although this voltage drops below 8V fairly rapidly, I am concerned that my design may damage the load switches.

Have you seen other applications with similar requirements as this one. Can you recommend a good solution? I am new to micro-controllers and am using an Arduino based platform. I am looking for simplicity. :)

Thanks, Mark

  • 0
    TI__Expert 5275 points

    Hi Mark,

     

    It is not recommended to exceed the absolute maximum rating of the device.  

    Although you might be able to leverage that the 8V maximum is with respect to the pin R2.  You could increase the R2 resistor so the R2 pin above ground when the device is enabled. Do be aware this will effect the ON/OFF pin threshold.

    There is still a problem when the device is disabled, R2 pin will get pulled to ground.  If the batteries are in series and above 8V, this could damage the device.  Will you be able to ensure the batteries are not in series configuration when the device is disabled?

     

    Regards,

    Adam Hoover

    DLS Applications

  • 0 in reply to Adam Hoover
    Prodigy 60 points

    Hello Adam,

    This is what I am trying to accomplish:

    Switch #1 is the problem child. During normal operation the batteries are connected in series and could be as high as 8.4V for a short period of time. While in charge mode the batteries are connected in parallel and the charge voltage doesn't exceed 4.2V. I did find an integrated load switch from Fairchild. The FDG6324L will handle an input voltage of up to 20V. I may look at some of your other charging solutions. I was thinking that you have an integrated multi-cell LiPo charger/balancer. If it had an integrated load switch it would be great.

    Mark

  • 0 in reply to Mark McCormack
    TI__Expert 5275 points

    Hey Mark,

     

    It seems the only way the TPS27081A would work is if you could ensure SW2 is in position 1 only when SW1 is already in position 1 (Load Switch Enabled).     As for a charging solution, I would recommend you copy & paste your last message into the battery management forum:

    http://e2e.ti.com/support/power_management/battery_management/f/179.aspx

     

    Best Regards,

    Adam