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BQ25892: EMC Design Improvements

James Susong
Prodigy 30 points
Part Number: BQ25892

What is TI's recommendation for P/N BQ25892 snubber design?  Also, what other EMI reducing techniques are there for this device beyond the Layout Guidelines in the data sheet?

  • 0
    TI__Mastermind 31250 points

    Hi James, 

    Thank you for reaching out via E2E. Please see my comments below regarding EMI suppression techniques for BQ25892. 

    1)Add a 1 nF capacitor at PMID, SYS, VBUS (optional), and BAT (optional). The purpose is to add this high frequency cap which works in 100MHz to 200MHz range 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