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Original question:

BQ25720: BQ25720RSNR

BQ25720: BQ25720RSNR: Output power issue

Udesh Singla
Intellectual 500 points
Part Number: BQ25720

HI 

We are facing the output in the battery charger. We are working on the laptop project based on intel alder lake 15W design in which we are using battery charger BQ25720RSNR.

Our board is rebooting when try to boot to the OS level. We have captured the output voltage of battery charger (VCC_VBATA), we found that there is dip in the output voltage till 6V due to which my complete system got rebooted. 

We have capture the waveform of the VCC_VBATA.

Below is the screenshot:

We have also capture the input voltage whether that is also dropping while VCC_VBATA drops, but there is no drop on the input voltage i.e VCC_BCHGR_IN

We have attached the waveform and schematic for your reference. Kindly check and help to resolve the issue.

6685.Battery_charger_schematic.pdfBattery charger output waveform.docx

  • 0
    TI__Mastermind 33445 points

    HI Udesh,

    Could you provide the register dump (all the register settings) after the event? Register 0x20 is charger status, which can tell us what happened in the charger. See below default settings. 

    Regards,

    Tiger

  • 0 in reply to Tiger Zhou
    Intellectual 500 points

    HI Tiger 

    We have captured the resistor dump when we are facing issue.

    0x12: 0xe70e
    0x14: 0x0700
    0x15: 0x3138
    0x20: 0x8000
    0x21: 0xb800
    0x22: 0x5000
    0x23: 0xc800
    0x24: 0x0000
    0x25: 0x0000
    0x26: 0x0000
    0x30: 0x3300
    0x31: 0x00b7
    0x32: 0x0434
    0x33: 0x4a81
    0x34: 0x41a0
    0x35: 0x2000
    0x36: 0x0048
    0x37: 0x006c
    0x3b: 0x09c4
    0x3c: 0x3c00
    0x3d: 0x3980
    0x3e: 0x5c00
    0x3f: 0x5000
    0xfe: 0x0040
    0xff: 0x00e1

    Also please let us know how we can set the battery charger output current. Is there any resistor which will configure the battery charger output ?

    we are suspecting that might be, battery charger configuration is not proper due to that it is not able to provide the sufficient output power.

  • 0 in reply to Udesh Singla
    TI__Mastermind 33445 points

    Hi Udesh,

    The register map looks fine. There is no resistor to program the charge current. It is a digital part, you can use charge current register to set the charge current. 

    I would suggest you monitoring the system current. You may be overload the charger. 

    Regards,

    Tiger

  • 0 in reply to Tiger Zhou
    Intellectual 500 points

    HI Tiger

    We have connected the power supply and measure the power required, so the required power is 12V/7A to start the system normally otherwise when system will try to boot , its restart automatically. Maybe charger is not giving the sufficient output power.

    Also can you please let us know how to handle the PROCHOT signals, what are the settign we need to do for Intel alder lake P 15W prcoessor.

    We want to enable PROCHOT functionality in our Battery Charger BQ27520 in our LAPTOP application to inform Processor of certain events. Kindly help us to find answers of mentioned queries-
    1)- In which events PROCHOT should be asserted.
    2)- These are the register dump that is set by default. kindly help us to enable the PROCHOT functionality in our application by setting proper bits in related register.
    0x12: 0xe70e
    0x14: 0x0700
    0x15: 0x3138
    0x20: 0x8000
    0x21: 0xb800
    0x22: 0x5000
    0x23: 0xc800
    0x24: 0x0000
    0x25: 0x0000
    0x26: 0x0000
    0x30: 0x3300
    0x31: 0x00b7
    0x32: 0x0434
    0x33: 0x4a81
    0x34: 0x41a0
    0x35: 0x2000
    0x36: 0x0048
    0x37: 0x006c
    0x3b: 0x09c4
    0x3c: 0x3c00
    0x3d: 0x3980
    0x3e: 0x5c00
    0x3f: 0x5000
    0xfe: 0x0040
    0xff: 0x00e1

    Please help us to resolve the issue

  • 0 in reply to Udesh Singla
    TI__Mastermind 33445 points

    Hi Udesh,

    Udesh Singla said:
    1)- In which events PROCHOT should be asserted.

    This is a question for customer. TI suggests enable all the PROCHOT events, such as PP_VDPM, ICRIT, INOM, IDCHG1, VSYS, BATPRES and ACOK except CMP. 

    Udesh Singla said:
    2)- These are the register dump that is set by default. kindly help us to enable the PROCHOT functionality in our application by setting proper bits in related register.

    Suggest REG0X34=0x41BF. 

    Regards,

    Tiger

  • 0 in reply to Tiger Zhou
    Intellectual 500 points

    HI Tiger

    We have connected the power supply and measure the power required, so the required power is 12V/7A to start the system normally otherwise when system will try to boot , its restart automatically.

    Maybe charger is not giving the sufficient output power.

  • 0 in reply to Udesh Singla
    TI__Mastermind 33445 points

    Hi, Udesh,

    To accommodate the system load,  you need to increase your current limit 0x3F to 5A, at the same time adjust the ILIM resistor divider to 5A. 

    Regards,

    Tiger

  • 0 in reply to Tiger Zhou
    Intellectual 500 points

    HI Tiger

    We have changed the input Rac resistor to 5mohm and now we are able to compensate our power and board is working, so can you please let me know is this configuration correct?

    Also do we need to change the 5mohm resistor in our input and output ?

    Also kindly let us know the RILIM resistor value according to 7A of output current

  • 0 in reply to Udesh Singla
    TI__Mastermind 33445 points

    Hi Udesh,

    5mohm is good. Just to clarify the RAC is input current limit resistor, while RSR is the charge current limit resistor. 

    The RILIM is only effective for input current, not the output current. There is an equation inside the datasheet to set the RILIM. See below.

    Regards,

    Tiger

  • 0 in reply to Tiger Zhou
    Intellectual 500 points

    HI Tiger, 

    Please let us know do we need to change the 5mohm resistor in both input and output side or only input side is sufficient.

    I mean, we can change 5mohm in input and 10mohm in output side. is it fine.

    Can you please confirm the RILIM resistor value as per 7A current. (I have calculated and it is coming around 191kohm)

  • 0 in reply to Udesh Singla
    TI__Mastermind 33445 points

    Hi, Udesh,

    Yes, you can change both resistors to 5-mohm. 

    Regards,

    Tiger

  • 0 in reply to Tiger Zhou
    Intellectual 500 points

    HI Tiger

    Please let us know the reason to change the output resistor to 5mOhm ?

  • 0 in reply to Udesh Singla
    TI__Mastermind 33445 points

    Hi Udesh,

    I thought you ask for it. Could you list your max input current and max charge current? Size the current sense based on the current.

    The rule of thumb is, 

    max current * current sense ~ 40-60mV, not to exceed 80mV. 

    Regards,

    Tiger

  • 0 in reply to Tiger Zhou
    Intellectual 500 points

    HI Tiger

    My max input current will be around 5A at 19.5V and the battery charger current will be around 1.8A only.

    Can you please confirm the RILIM resistor value as per 7A current. (I have calculated and it is coming around 191kohm)

  • 0 in reply to Tiger Zhou
    Intellectual 500 points

    HI Tiger

    Yes this is confirmed.