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TPS54360B: Battery Power flow into SW PIN of TPS54360B

Part Number: TPS54360B
Other Parts Discussed in Thread: TPS54360

Hi Team,

My setup,
Vin->TPS54360B->Battery Charger | Load | LDO

Functionality:

Q8 is OFF when Vin is ON and TPS5360B is giving an output.

Q8 is ON when there is no output form TPS54360B.

My issue:

Question 1:

When Q8 is ON, the battery voltage will reach PIN 8 SW of TPS54360B and also the PIN 1&2 of battery charger IC,

Is there is any possibility that the battery voltage that is of Li-ion battery of 4.2V max at PIN SW of TPS54360

might damage the TPS54360B IC and affect its ON operation in any way?

Question 2:

Do we need to protect the TPS54360B PIN 8 SW from any voltage source connection?

Kindly clarify,

Many thanks

Swaroop

  • Hi Swaroop,

    I'm not sure I understand your circuit.

    Why is VOUT of the TPS54360B connected directly to the load? I can't speak on behalf of the battery charging section, but shouldn't the battery charger IC be in charge of turning on and off current to the battery? The way the circuit is constructed now, it looks like the TPS54360B will just provide current to the battery.

    Thanks,

    Andrew

  • Dear Andrew,

    Thanks for your reply,

    Let me share the Working Logic:

    1. TPS54360B supplies power to the load when Vin is available, Q8 is OFF

    2. TPS54360 also supplies power to the battery charger IC and internal battery gets charged when Vin is available. Q8 is OFF

    3. When Vin is absent, internal battery supplies power to the load. Q8 is ON

    My issue is,

    When Vin is absent, Q8 turns ON, and internal battery supplies power to the load,

    the battery voltage (Vbat=4.2V max) will appear at PIN 8 SW of TPS54360B.

    Question 1: So will this battery voltage (Vbat=4.2V max) at SW PIN of TPS54360B damages the TPS54360B IC?

    Question 2: Will the SW PIN of TPS54360B sink any current when Vin is absent and battery voltage (Vbat=4.2V max) appears at it?

    Kindly support and clarify.

    Thanks and reagrds

    Swaroop

  • Hi Swaroop,

    Thanks for your explanation of the the mosfet. I understand now.

    You should be ok as long as you don't violate this value:

    It shouldn't sink any voltage if VIN is absent as BOOT shouldn't be charged, so the internal mosfets should be turned off.

    Thanks,

    Andrew

  • Dear Andrew,

    Thank you for your reply.

    The battery voltage is 4.2V max only, so we well within the limits.

    Thanks for your support.

    Warm regards

    Swaroop