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BQ24192: GPS Signal loss and interference

Darshan Panchal
Prodigy 10 points
Part Number: BQ24192

Hello i have used BQ24192 as a Power management Chip in my Embedded Product.

In my product BQ24192 do battery charging of 3.7v 1100 mah battery and also drives module as a main supply.

I am using SIM808 module which have GSM and GPS inbulilt.

I give the power directly from LI-ION battery 3.7v to my Board then GPS works Good.

But if i connect Supply from BQ24192 Output then my GPS performance and signals Degrades about 40 %

I have attached My power section schematic.

Please any one guide me to troubleshoot my problem.

Thanks .POWER IC.pdf

  • 0
    TI__Expert 8230 points

    Hello Darshan,

    From your schematic, I see you only have 0.1uF on PMID. Please note that the capacitance at PMID is very critical since PMID is the actual input to the switching converter, so you want to make sure enough capacitance is there to handle the high frequency return current on PMID. You can add a 10uF cap on PMID since the device is in default mode and the default charge current is 2A.

    Another point is the EMI: if your application is EMI sensitive, routing and component placement is crucial to help mitigate EMI. The first step is to revise the layout complies with the layout guidelines on the datasheet. After this, you can add 0402 1nF high frequency capacitors that work effectively between 100MHz and 200MHz on PMID and SYS. 

    Slowing the SW slew rate by adding a snubber can help reduce EMI at a trade-off of efficiency. 

    Other customers also add shielding over the switching converter in EMI sensitive applications.

    I suggest starting by adding more caps on PMID and revising PCB layout and then moving on to adding additional components.

    Hope this helps.