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Problem with I2C and boost mode in Bq24295

Other Parts Discussed in Thread: BQ24295

Hello all,

I have developed my own board using BQ24295,  but i got some trouble while running.

1) I could not read register except for REG09 and REG0A on I2C. For all other register i am getting 0XFF .My I2C code for reading register is as per follow.

start bit,salve address in write mode,ACK, register address, ACK , start bit, slave address in read mode, ACK, data@register address, NACK, Stop bit

Please let me know if there any step missing in the above sequence .

2) Boost mode is not working properly even-though all pin are set as per datasheet.

  • Hi,

    The first thing to understand is why you cannot communicate with the device.  What are you using to communicate with the device?  Please check your custom code as well because it's unusual that you can read two registers, but not the others. 

    Please try using a known good solution to communicate such as the TI provided software (http://www.ti.com/product/BQ24295/toolssoftware) with the USB-to-GPIO adapter (http://www.ti.com/tool/USB-TO-GPIO) used to communicate with standard EVM.

    Complete details on the communication protocol for the bq24295 are provided in the datasheet starting on page 33 under the heading Serial Interface.  

     

    Thanks,

    Rachel 

  • Hi Rachel,

    Thank you for your response,

    Yes i understood why i couldn't communicate with the device using I2C. Now It  is working properly.

    but still i couldn't  get boost converter output properly .On PMID pin i  am getting only 3.15V without any load while according  to default condition it should be 5.126V.

    My schematic diagram is the same as given in EVM.

    Please suggest  me any solution .

    Regards,

    Hardik

     

  • Hi Hardik,

     

    What is the status of REG08 and REG09?  Please also review the section "Boost Moode Operation from Battery" starting on page 21 of the bq24295 datasheet and verify that your set-up meets all of the conditions required for boost mode operations including:

    1. BAT above BATLOWV threshold (VBATLOWV set by REG04[1])
    2. VBUS less than BAT+VSLEEP (in sleep mode)
    3. Boost mode operation is enabled (OTG pin HIGH and REG01[5:4]=10)
    4. After 30ms delay from boost mode enable

     

    Best,

    Rachel 

  • Hi Rachel,

    I have changed my PCB designed and i got boost converter output 5.2V. But OUTPUT on PMID pin is stay stable for some time and when load of 500mA  is connected it decreased(3.5V).

    Status of REG08 is 0x00 and REG09 is 0x80 and mentioned conditions required for boost operations are satisfied perfectly.

    My schematic is same as given in EVM but PCB is of 2 layer and 3.3V for controller is generated by LDO.

     

     Regrds,

    Hardik

  • Hardik, 

     

    Thank you for your patience over the holiday season. 

    REG09 = 0x80 is Watchdog timer expired which will reset the register values.  Please disable the watchdog for testing purposes, or be sure to maintain proper device communication to prevent timeout. 

    A 4-layer PCB is recommended for best OTG load regulation, but it is possible to use a 2-layer solution if special care is taken in the layout and board stack-up.  Please reference the bq24295 2-layer EVM user guide for layout and stack up recommendations as well as test results:  http://www.ti.com/lit/ug/sluuao5b/sluuao5b.pdf 

    In particular page 2, Figure 1 has a detailed chart showing the effect of different layouts and stack-ups on OTG load regulation.  

     

    Best,

    Rachel 

      

  • Hi Rachel,

    I have designed charger product using BQ24295 as per given schematic.

    Battery charging circuit and Boost converter part is working perfectly when both are connected separately. 

    When i connect the load of 5W at PMID pin, I am getting 1A current at OUTPUT and battery is charging at 1A current. Within sometime, battery charging stops. However, I get output on PMID pin. After sometime, battery starts charging automatically. 

    It looks like that IC has some charging cycle due to which charging stops and auto-starts.

    When i remove load on PMID pin battery is charging properly. Auto start-stop issue is not seen.

    I need continuous output at both -BAT and PMID pins together. Kindly help to resolve the issue.

    Regards,

    Hardik Dhameliya

  • Could you please read the register values  when you tried different test conditions? Especially for REG08 and REG09. Please check if there is anything abnormal.

    Thanks!