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BQ25622E: Radiated Emission Measurement Fail

hitesh soramiya
Prodigy 145 points
Part Number: BQ25622E

Tool/software:

Hello, we are using the BQ25622ERYKR for battery charging. We have tested radiated emissions on our custom board, and the results are fail reports attached below.

Could you please check the reports and tell us why the PCB is non-compliant in charging mode at specific mid-band frequencies (333 MHz, 381 MHz)?

In device on condition reading are under the range.

Looking forward to your response.  

  • 0
    TI__Mastermind 31090 points

    Hello Hitesh, 

    Thank you for reaching out via E2E. Do you use any EMI suppression techniques in your custom board design? Below are a few options we suggest to try if you have not already implemented. 

    1)Add a 1 nF capacitor at PMID, SYS, VBUS (optional), and BAT (optional). The purpose is to add this high frequency cap to return high frequency noise to GND. 

    2)Add snubber circuit (resistor and capacitor) from SW pin to GND. Use R = 1ohm and C = 15 nF as reference, but TI recommends to try several different combinations to get best results with your custom PCB design. 

    3)Add resistor (in range of 0 ohm to 5 ohm) in series with BTST capacitor from BTST pin to SW pin. The purpose is to reduce the switching slew rate. We do not recommend using higher resistors values than 5 ohm as it will start to adversely affect converter efficiency.

    Best Regards,

    Garrett 

  • 0 in reply to Garrett Kreger
    Prodigy 145 points

    Hello Garrett,

    If we change  PFM_FWD_DIS bit to Disable it will help?

    Because its happen when load is not connected.

     

  • 0 in reply to hitesh soramiya
    TI__Mastermind 31090 points

    Hi Hitesh, 

    By setting PFM_FWD_DIS = 1 PFM (pulse frequency modulation) switching will be disabled. Figure 9-8 in the datasheet provides an example of PFM switching compared to PWM switching. At light load conditions PFM switching will be at a lower frequency compared to if PWM switching is forced by disabling PFM. 

    It may help improve your test results, but I cannot say for certain it will help reduce the mid-band EMI you are observing. 

    Best Regards,

    Garrett