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BQ25700A: Current oscillated by different input current setting

Beginner
Intellectual 2431 points
Part Number: BQ25700A

Hi Team,

Please refer to the attached image. When customers perform a performance testing, they found there is a current oscillated (Red region). After changing the register 0x3F – input current limit from 1500 to 2500mA, this symptom is gone.

Attach two settings for your reference. Kindly let me know the root cause for this.

  • 0
    TI__Intellectual 2431 points

    Fullscreen bq25700-ACP1000-20190618.txt Download 
    * Created: Wed Aug 07 10:16:12 CST 2019
*
* Format: Register Name  tab Character,\t  Hexadecimal register value.
* Device: bq25700A
* BQZ Container: Charger_1_00-bq25700A.bqz
*
Charge Option 0	820E
Charge Current Register	0000
Charge Voltage Register	3140
OTG Voltage Register	0000
OTG Current Register	0000
Input Voltage Register	1100
Minimum System Voltage	1D00
Input Current Register	3200
Charge Status Register	2000
Prochot Status Register	0000
Input Current Limit In Use	3200
VBUS and PSYS Voltage Read Back	5900
Charge and Discharge Current Read Back	0000
Input Current and CMPIN Voltage Read Back	0000
System and Battery Voltage Read Back	0000
Manufacture ID Read Back	0040
Device ID Read Back	0079
Charge Option 1	0210
Charge Option 2	02B7
Charge Option 3	0000
Prochot Option 0	4A54
Prochot Option 1	8120
ADC Option	2000
    Fullscreen 190521-25700setting.txt Download 
    * Created: Tue May 21 18:17:14 CST 2019
*
* Format: Register Name  tab Character,\t  Hexadecimal register value.
* Device: bq25700A
* BQZ Container: Charger_1_00-bq25700A.bqz
*
Charge Option 0	820E
Charge Current Register	0600
Charge Voltage Register	3140
OTG Voltage Register	0000
OTG Current Register	0000
Input Voltage Register	1140
Minimum System Voltage	1000
Input Current Register	2100
Charge Status Register	AC00
Prochot Status Register	0000
Input Current Limit In Use	2100
VBUS and PSYS Voltage Read Back	5A00
Charge and Discharge Current Read Back	1600
Input Current and CMPIN Voltage Read Back	1F00
System and Battery Voltage Read Back	008F
Manufacture ID Read Back	0040
Device ID Read Back	0079
Charge Option 1	0210
Charge Option 2	22B7
Charge Option 3	0000
Prochot Option 0	4A54
Prochot Option 1	8120
ADC Option	A015

  • 0 in reply to Beginner
    TI__Expert 3320 points

    Hi There:

        In order to understand this correctly, we would like to know what is the vertical and horizontal axis in your plot. Please also add the input voltage, battery voltage, system voltage and load current information. 

    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

    Shishuo

  • 0 in reply to Shishuo Zhao
    Prodigy 10 points

    Hi Shishuo

    Customer has a problem about current oscillation when in CV mode. Below is their charger condition.

    input voltage limit : 9000mV

    input current limit: 1500mA

    Charging Voltage 12600mV

    Charging Current 1500mA

     

    However, they have two solutions to solve this abnormal case but they are uncertain if it has any side effect. So customer would like to know what charger behavior at that moment is.

    1. add more 47uF on Vsys or VBAT

    2. Set Input Current Limit to 2500mA.

  • 0 in reply to shane ke
    TI__Expert 3320 points

    I think work around 1 is better, because Input current limit is used to preventing overloading adapter.We set it to be 1.5A according to the adapter spec I believe.

    Regards

    Shishuo

  • 0 in reply to Shishuo Zhao
    Intellectual 255 points

    Hi Shishuo,

    Thanks for update. Could you please let us know why the charging current has large oscillation while charger is in CV mode? 

  • 0 in reply to Shane Ke
    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
    Intellectual 255 points

    Hi Shishuo,

    Thanks for update. Could you please let us know why the charging current has large oscillation while charger is in CV mode?

  • 0 in reply to Shane Ke
    TI__Expert 3320 points

    Hi There:
      

         I suspect this may be related to the PFM mode. You can try to add 68nF cap between SRN and SRP pins on the EVM to see if there is any improvement. 

    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,