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BQ24195: BQ24195 add wireless charge failure

Part Number: BQ24195

Hi

My customer design pad with the NE6101 wireless receiving IC to charge BQ24195 encountered the following problems, please help analyze

The power of the wireless receiving IC is 10W (9V, 1.1A) or 5W (5V, 1.1A), but it will always be dragged down by BQ24195.

1. Under normal circumstances, the input current limit is 1.2A, and the charging current is limited to 1.6A. However, the instantaneous input current is as high as 1.7A when the actual measurement is charged, and the wireless receiving IC is disconnected from the TX terminal due to power overload.

2. The input current limit is 0.5A, and the charging current is limited to 0.5A. However, the actual input current is about 1.5A when the actual measurement is charged, and the input current limit register will become 1.5A by itself.

3. The input current limit is 0.9A, and the charging current is limited to 0.5A. However, the actual input current is as high as 1.5A when the charging is actually measured, and the input current limit register does not change.

4. The input current limit is 0.15A, and the charging current is limited to 0.5A. However, the actual input current is as high as 1.7A when the actual charging is measured, and the input current limit register will become 1.5A by itself.

5. The input current limit is 1.5A, and the charging current is limited to 0.5A. However, the actual input current is as high as 1.7A when the charging is actually measured, and the input current limit register does not change.
In the above case, the input voltage limit is 4.52V, so I hope to help solve the problem of large current during charging. This will delay the wireless charging or the power is not enough to reach 9V, 1.1A output; the result will be continuous charging and Power off
Waiting for your reply
Thanks
Star
  • Hi Star,

    I do not expect those input current numbers above unless there is a load on SYS.  We have not seen similar issues when the BQ24195 is powered by a TI wireless RX. I am searching for data to send.

    There will be a spike of current when the charger first turns on in order to charge up the capacitors and the inductor.  The IINDPM and VINDPM loops respond in the 100us-1ms time frame.  

    Have you tried increasing the VINDPM threshold to only slightly below the RX output?  Can you increase the capacitance between the RX output and charger VBUS to mitigate the start up spikes?

    Regards,

    Jeff

  • Hi Jeff

    Thanks for your help.

    Did you mean SYS has a load and there will be a  transient current.

    We also try to increase the VINDPM threshold to just below the RX output, but the input power will decrease.

    Thanks

    Star

  • Hi Star,

    Is there a dc load or transient load on SYS that is causing the charger's input current to spike?

    Regards,
    Jeff

  • Hi Jeff

    Yes, SYS is the power input source of the tablet, so is there any method to solve it?
    Thanks
    Star
  • Star,

    The BQ24195 response time and inrush current cannot be changed internally.  The only solution is to use additional capacitance at either the charge input or the SYS output to better handle the current spikes that appear to be crashing the wireless adapter.

    Regards,

    Jeff