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Original question:

BQ25883: Noise in Inductance

BQ25883: Issue about Vsys is inexact and charge efficiency is too low

Troyson Li
Expert 2455 points
Part Number: BQ25883

Hi Team ，

         My customer used BQ25883 and there are 3 issue.Can TI help to solve it ? Thank you!

         1.The Ichg offset seems to be 0mA rather than 100mA which mark in the specification

        

         2. We found the Vsys is inexact when we disable charge(Write 0 to REG06_BIT3 (Chage disable)) in both of EVM & our borad. In our test. The Vsys is 6.98V (with system 100mA load) while the SYS_MIN is 6.8V which set in REG07

         3. We found the charge efficiency is too low in our board (Vin=5V/Ichg=960mA/Isys=30mA). Do you help some suggestions to improve the efficiency?

        Thanks!

  • 0
    TI__Mastermind 29965 points

    Dear Troyson,

    First, the definition of offset is as follows. If you set every charge current register to 0, you will get the offset value.

    Second, if you look at Figure 5 of the datasheet, you will see that at 300 mA SYS load, you expect a 200 mV offset. I expect this to follow to lower load currents. This is also specified in the datasheet below.

    Third, can you give me some more specifics? What is the input current? How are you calculating efficiency?

    Thanks,

    Mike Emanuel

    Please click "This resolved my issue" button if this post answers your question.

  • 0 in reply to Michael Emanuel35
    Expert 2455 points

    Hi Michael，

            Understood your clarify about Issue 1&2. And The following pcb are the scb&pcb.  The inductor they used is murata DFE2520 which Q is 37 in 1Mhz and the Q in EVM is 80. Thank you!  

            

            

     

  • 0 in reply to Troyson Li
    TI__Mastermind 29965 points

    Dear Troyson,

    Before I can evaluate your efficiency problems, I need to know your input current, input voltage, battery voltage, system voltage, battery current, and system current. More importantly, I need all of these measurements at the same set of conditions when you are trying to calculate efficiency. In addition, I need to know how you are calculating efficiency.

    Thanks,

    Mike Emanuel

    Please click "This resolved my issue" button if this post answers your question.

  • 0 in reply to Michael Emanuel35
    Expert 2455 points

    Hi Michael . 

           Customer is out of office this week. I will reply you with the required information once customer comes back to work.Thank you!