• State Resolved
  • Locked Locked
  • Replies 2 replies
  • Subscribers 64 subscribers
  • Views 782 views
  • Users 0 members are here
Support feedback
Options
Options
Related

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

BQ24617: Many Question for the schematic

Jerry Chu
Genius 4915 points
Part Number: BQ24617

Hi Expert,

1. For two cells application, if I choose 3Mohm and 1Mohm for the FB resistors, does it ok for the design?

2. For the Cff Cap, the datasheet shows 22pF, what's the range?

3. Cff is parallel in Rtop in FB, if we add a Cap 0.1uF and parallel in Rbot, seems the battery detection waveform is wrong. Can you guide me what's happening?

If the battery pack was UVP, seems the waveform can trigger the pack, but any risk for it?

4. Customer wants to prevent the EMI issue, so add the bead at the below circuit. After that we can't get the battery detection waveform, seems the bead consumed the Iwake, I did it in EVM and got the same result.

If we add the 10uF before the bead, that can get the right waveform. Any suggestion for the bead circuit and why the bead consumed the Iwake? 

Thanks!

  • 0
    TI__Genius 16185 points

    Jerry,

    My suggestion for your questions are as following.

    1. There is leakage current from FB pin and around 100nA, so I think too high feedback resistor divider will increase tolerance. So if there is no big power consumption concern, I will suggest resistor divider total impedance value should be lower than 1Mohm as EVM board used.

    2. Cff can improve transient performance, in general, 22pF is our suggestion value to use in EVM board. as for suitable value is dependent on resistor divider, PCB layout and loading condition. So will suggest to fine tune based on real system evaluation.

    3. This cap in FB should be influence battery absent detection. Please measure FB pin voltage to compare the waveforms with and without this cap. Then you will know the reason.

    4. for battery absent detection, charger has circuit to charge(125mA) and discharge(8mA) output caps. Then IC will based on BAT side voltage status to judge battery is absent or not. This bead will impact charge and discharge speed to cause false judgement.

    Thanks

  • 0 in reply to Paul Yeh
    TI__Guru 57621 points
    We haven’t heard back from you for a while. We are assuming that you were able to resolve the issue. If not, just post a reply below or create a new thread if the thread has locked due to time-out. Thanks!
    Please click "This Resolved my issue" button if this post answer your question.