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Original question:

BQ24715: Can the mode of OVP and OCP be setting?

BQ24715: OCP Setting problem

Lumina Gui
Expert 2815 points
Part Number: BQ24715

Hi TI Teams,

When we testing the OCP function of BQ24715, we only connected the adapter without the battery (3-cell Li-ion battery), the OCP did not works when VBATA was pulled to about10A, which resulting in the EU5 MOS burned out.

The schematic is shown as below:

BQ24715 SCH.pdf

So we have the below question about the OCP of BQ24715:

1.We want to set the OCP threshold at about 6A, so whether the LSFET OCP threshold can be adjusted below 250mv? From the datasheet we can learned that the LSFET OCP threshold only has two level, 350mV (default) and 250mV (SMBUS setting).

2. Only connect the adapter, and set the input current limit to 2.8A (0x3Fh=0x0AF0, 0x12bit [7]=0). And we trying to pull load to 70W at the VBATA end, when the input current up to 3.6A, the back-to-back MOS(EU5) did not turn off, that means the OCP function does not work. However, the input current limit setting is valid when both the battery and the adapter are connected.

3. Only connect the adapter, and set the input current limit to 3.2A (0x3Fh=0x0000,default value), ACOC setting to 333% IDPM (0x12 bit[7]=1). When we trying to pull load to 40W at the VBATA end, the MOSFET turned of when the input current rise to 2.4A, the protection point is too low.

 

We want to know why this problem occurs and how to setting the OCP function, can you give us some suggestion for this?

Thanks,

Kind Regards

  • 0
    TI__Genius 12505 points

    Hello Lumina, 

    Lumina Gui said:
    We want to set the OCP threshold at about 6A, so whether the LSFET OCP threshold can be adjusted below 250mv?

    No, the LSFET OCP can not be adjusted below 250mv.

    Lumina Gui said:

    2. Only connect the adapter, and set the input current limit to 2.8A (0x3Fh=0x0AF0, 0x12bit [7]=0). And we trying to pull load to 70W at the VBATA end, when the input current up to 3.6A, the back-to-back MOS(EU5) did not turn off, that means the OCP function does not work. However, the input current limit setting is valid when both the battery and the adapter are connected.

    3. Only connect the adapter, and set the input current limit to 3.2A (0x3Fh=0x0000,default value), ACOC setting to 333% IDPM (0x12 bit[7]=1). When we trying to pull load to 40W at the VBATA end, the MOSFET turned of when the input current rise to 2.4A, the protection point is too low.

     

    The OCP function of BQ24715 should work when only the adapter is connected. Can you provide more information on your setup:

    Can you provide me with all of the register values?

    What is the adapter input voltage?

    How much current is the load pulling?

    Did the input current increase to 3.6 A on it's own when the load was applied and the input limit was still 2.8A?

    Thanks,

    Kind Regards

     

  • 0 in reply to Christian Moyer
    Expert 2815 points

    Hi Christian,

    Pls check the below information for your question.

    1)Can you provide me with all of the register values?

     A: The register values as the below with only connect the adapter:

    Charge Options Register (0x12H) 0x645E(AC&BAT IN) 0x645C(only AC IN)
    Max Charge Voltage Register (0x15H) 0x3390
    Charge Current Register (0x14H), 0x07D0
    Input Current Register (0x3FH) 0x0AF0
    Minimum System Voltage Register (0x3EH) 0x2400

    2)What is the adapter input voltage?

    A: 19V

    3)How much current is the load pulling?

    A: VBATA end pull to 8A and got not protection.

    4)Did the input current increase to 3.6 A on it's own when the load was applied and the input limit was still 2.8A?

    A: Yes.

    We just want to adjust the OCP output of VBATA to about 6A (currently the OCP protection point is too high, and the MOSFET will be burned down with the OCP testing), and how to adjust the ocp point?

    Thanks,

    Kind Regards

  • 0 in reply to Lumina Gui
    TI__Genius 12505 points

    Hello Lumina,

    According to section 8.3.4 Input Over-Current Protection (ACOC) of the datasheet:

    According to section 8.5.1.3 Setting Charger Options of the datasheet:

     Based on this information the OCP output of VBATA can not be lowered to 6A.

    Regards,

    Christian