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BQ24104: BQ24104R EMI ISSUE

Hsu cheng
Expert 1565 points
Part Number: BQ24104

My customer is using the BQ24104R to measure EMI at 70MHZ over spec , please help us to provide suggestions for modification.

The PCB circuit ,layout and test report  of input 5V output 4.2V0.4A is as follows.

230HF-R2-5V1.5A.pdf

115VF-R2-5V1.5A.pdf

115HF-R2-5V1.5A.pdf

TP2版本(PCB LAYOUT圖).pdf

SCH-TP3.pdf

  • 0
    TI__Guru**** 166916 points
    Hi Hsu,

    The placement of the input capacitors to the power FETs for the buck are the most critical for low EMI. After reviweing the PCB layout, I see that the decoupling capacitors (C107/118-120) are placed the furthest from the INx pins and have a long return to GND. Also, the connection to INx and GND are very thin. I suggest relaying out the board with at least 1 decouping capacitor and the bulk capacitor at the and of the IC (out from pins 1 and 20). This placement will allow for the smallest current loop. Also, I suggest much wider traces and/or a copper pour or fill when connecting to the INx and GND pins.

    Regards,
    Jeff