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SN65DP159 - 0.01uF cap for VDD pin

Kawai
Guru 19785 points
Other Parts Discussed in Thread: SN65DP159

Hello Team,

Please allow me to ask you about the cap for VDD=1.1V. In the User's Guide, I found five 0.1uF caps, one 0.01uF cap, and 10uF. I believe 0.1uF should be placed closed to each VDD1-5 pin, however, where should you place the 0.01uF cap ? Which VDD pin would be the power for high speed signal ? Please tell us your recommendation.

I could not read this 0.01uF cap from the layout in the User's Guide.

Best Regards,

Kawai

  • 0
    TI__Mastermind 23815 points

    hi Kawai-san,

    In our EVM for both DP159RSB and DP159RGZ capacitor C22 is close to VDD1 (Pin 12 and Pin 14 respectively).

    Regards

  • 0 in reply to Moises Garcia
    Guru 19785 points

    Hello Moises-san,

    Thank you for the answer.
    I found that Figure 31/32 in the datasheet has different cap value compared to User's guide. Which would be the TI recommendation ? If the datasheet is the recommendation, please teach us how to place each caps.

    Best Regards,
    Kawai

  • 0 in reply to Kawai
    TI__Guru 60870 points

    Hi Kawai,

    I would recommend using two 0.01uF capacitors on the VDD rail.  We have found better noise reduction with varying the values of the decoupling capacitors rather than using all the same value.  Please note that all VDD pins connect inside the SN65DP159 so it does not matter which decoupling capacitor values go with which VDD pin, but we recommend that each pin have at least one decoupling capacitor.

    Thanks,

    JMMN

  • 0 in reply to JMMN
    Guru 19785 points
    Hi JMMN-san,

    Thank you for the information that all VDD pins are tied together internally. Yes, we will recommend to use total two 0.01uF caps to VDD pin and 0.1uF to each pins.

    Best Regards,
    Kawai