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Reverse Battery Protection for the TPS65070?

MikeH
Guru 15580 points
Other Parts Discussed in Thread: TPS65070

Can someone give some advice and example circtuit for protecting the TPS65070 against reverse batery insertion? It appears to be a problem since the TPS65070 shares both the charging path and the load path of the battery with 2 pins that are connected together interlally in the chip.

Thx,

MikeH

 

  • 0
    TI__Mastermind 36110 points

    I have attached a link to an application note that provides several potential solutions to protect against reverse battery insertion.

    http://focus.ti.com/lit/an/slva139/slva139.pdf

  • 0 in reply to Matthew Day
    Guru 15580 points

    Michael,

    I appreciate your taking time to reply to my question. I do not appreciate your taking the liberty of marking it at "answered" because it is not. Please let me do that.

    First of all, I assume with your forum rating you are fairly knowlegable in this subject. Secondly, if you had taken the time to read the details of my post you will see that the app note (which I have already read) do not solve my specific problem with the TPS65070. The problem is that the "charge path" and the "load path" are shared by the same pin on the PMIC. A diode in the load path (as proposed by the app note) will prevent the battery from being charged.

    Surely someone has solve this problem......?

    MikeH

  • 0 in reply to MikeH
    TI__Mastermind 36110 points

    I'm glad to know that you already read the application note.  I'm sorry that it didn't provide the information you needed.  I appologize for prematurely marking the thread as "answered".  It is very rare that the person asking the original question marks the thread as answered after the question is resolved.  Because of this, we often mark it answered when we reply, knowing that the person can always reject the answer if they need  more information or clarification.

    You are correct that the solutions in the application note will not work for the specific application you are asking about. The application note addresses reverse battery insertion for primary cells powering a system.  Examples of primary cells are AA Alkaline that do not need charging.  There are two commonly used solutions to protect against reverse battery insertion of a Li-Ion battery on the output of a charger with dynamic power path management (DPPM).  The first is to mechanically key the battery connector so it is impossible for the customer to incorrectly insert the battery.  This the most common solution.  Examples are the Li-Ion batteries in all cell phones,  camcorders, etc.  Another solution is to add a diode to the BATT pin.  Connect the anode to ground and connect the cathode to BATT.  In normal operation, the diode is reversed biased and does not affect operation of the circuit.  If a battery is installed backwards, the diode turns on and prevents the battery from damaging the battery charger.  The diode effectively short circuits the battery, but this should be acceptable because the Li-Ion battery should have build in short circuit protection.

  • 0 in reply to Matthew Day
    Guru 15580 points

    Michael,

    Michael Day said:
    Another solution is to add a diode to the BATT pin.

    Brilliant! Add a small fuse and you can also protect the battery.

    Sorry for being so hard on you, but I find some folks on the forum assume that people asking questions have not done their homework, when indeed thay have (self included).

    Thanks.

    MikeH