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DS125BR111: Decoupling capacitor for VDD

TerryU
Prodigy 145 points
Part Number: DS125BR111

Hi Experts,

I use DS125BR111 on 3.3V mode, and I would ask a decoupling capacitor's value.

I look a datasheet and it is described "3.3V mode, decouple each VDD pin with 0.22uF cap to GND." in the Pin Functions table. On the other hand it is described "Place 0.1μF capacitors close to VDD Pins. Total capacitance should be ≦ 0.2 uF" in power Supply Recommendation. The description is different from each other. Which is correct? And if later one is correct, what will it occur with large capacitance exceeding 0.2uF.

Regards,

Tetsuya, 

  • 0
    TI__Mastermind 28090 points

    Hi Tetsuya,

    Thank you for pointing out this inconsistency in the datasheet. My suggestion is to follow the Power Supply Recommendations section and place one 0.1uF capacitor per VDD pin. Note that there is some flexibility in decoupling schemes that will work with DS125BR111, as the EVM implements a single 0.1uF capacitor for both VDD pins. Using decoupling capacitors with larger value could potentially allow higher frequency noise to reach the internal power supply. Ultimately the best way to confirm a decoupling scheme's performance is via simulation.

    Best,

    Lucas

  • 0 in reply to Lucas Wolter
    Prodigy 145 points

    Hi Lucas,

    Thank you for your rapid response. I will note your suggestion.

    Regards,

    Tetsuya