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BQ25703AEVM-732: Problem with OTG in single cell config

Jarek Peroutka
Prodigy 90 points
Part Number: BQ25703AEVM-732

Hi,

in one of our products i need to provide 10V and 400mA in OTG mode. The connected battery is a 30Ah 1S Lipo battery.

When connecting the load (a 25 Ohm power resistor) the OTG voltage drops to 3V or Charger disables OTG and the OTG_OCP bit is set. This behavior occurs at a voltage above 8V, below 8V everything works fine. The strange thing is the battery voltage measured by the charger also drops to 3V but measured with an multimeter it is still at 3.8V.

According to the datasheet even 20V and 400mA should not be a problem.

Pleas help.

Regards,

Tom

  • 0
    TI__Expert 3320 points

    Hi Tom:
        

         In order figure out the root cause I would like to know:

         1, How much OTG current setting do you put into 3Ch register? Is it higher than 400mA? This is the OTG current limitation register, you need to configure it correctly.

         2, For sanity check, please make sure the battery power supply current limit is higher than 3A for this test.

         3, If above doesn't work, please increase battery voltage a little to 4.2V and see if the issue still exist. 

    Regards

    Shishuo

  • 0 in reply to Shishuo Zhao
    Prodigy 90 points

    Hi Shishuo:

    I have tested with different OTG current settings (between 400mA and 2A) it always behaves the same. 

    Yes the maximal current of the supply is 5A. 

    On 4.2V the charger is able to supply 300 mA but still not the desired 400mA.

    In the attachment you can se my register configuration.

    Regards

    Tom

    Fullscreen otg_test.txt Download 
    * Created: Tue Aug 27 10:28:59 CEST 2019
*
* Format: Register Name  tab Character,\t  Hexadecimal register value.
* Device: bq25703A
* BQZ Container: Charger_1_00-bq25703A.bqz
*
Charge Option 0	020E
Charge Current Register	0000
Charge Voltage Register	1060
OTG Voltage Register	1600
OTG Current Register	2500
Input Voltage Register	0000
Minimum System Voltage	0900
Input Current Register	4100
Charge Status Register	B100
Prochot Status Register	0000
Input Current Limit In Use	2500
VBUS and PSYS Voltage Read Back	6A00
Charge and Discharge Current Read Back	0000
Input Current and CMPIN Voltage Read Back	0023
System and Battery Voltage Read Back	1312
Manufacture ID and Device ID Read Back	7840
Device ID Read Back	1178
Charge Option 1	0211
Charge Option 2	0235
Charge Option 3	1000
Prochot Option 0	4A54
Prochot Option 1	8100
ADC Option	A0FF

  • 0 in reply to Jarek Peroutka
    TI__Expert 3320 points

    Hi Tom:
        

         I checked you register setting, please confirm you set REG32<5>=1 and test again. By the way are you testing on our TI EVM? 

    Regards

    Shishuo

  • 0 in reply to Shishuo Zhao
    TI__Expert 3320 points

    Hi there,

    We haven’t heard back from you. We are assuming you were able to resolve your issue. If not, just post a reply below or create a new thread if the thread has locked due to time-out.

    Regards,

  • 0 in reply to Shishuo Zhao
    Prodigy 90 points

    Hi,

    yes REG32<5> is set to one and yes i am testing on the TI EVM.

    The problem is still there and i have noticed that the the chager enters OTG OCP when the battery voltage drops below 3.45V even without a load on OTG.

    Can you confirm this behavior or do i need to set any registers?

    Regards,
    Tom 

  • 0 in reply to Jarek Peroutka
    TI__Expert 3320 points

    Hi There:
        

         I believe the OTG is disabled because the BAT voltage is lower than 3.2V. We define disable OTG if battery voltage falls below 3.2V , this is included in the data sheet battery under voltage lockout section.

         You also side the charger read back battery voltage is already 3.0V, you can check the SRN pin voltage to see if it is around 3.0V.

    Regards

    Shishuo

  • 0 in reply to Shishuo Zhao
    TI__Expert 3320 points

    Hi there,

    We haven’t heard back from you. We are assuming you were able to resolve your issue. If not, just post a reply below or create a new thread if the thread has locked due to time-out.

    Regards,