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UCD3138064: Why do not use bead to connect between V33A and V33D ?

ken yao
Prodigy 160 points
Part Number: UCD3138064
Other Parts Discussed in Thread: UCD3138

Hi,

Why do not use bead to connect between V33A and V33D ?

is there any issue ?

  • 0
    Prodigy 160 points
    Hi ,
    Another question.
    What is the function of resistor to connect between V33A and V33D ?
    Why 1 ohm is the best choice ?
  • 0 in reply to ken yao
    TI__Mastermind 18370 points

    A resistor between V33A and V33D together with the capacitor acts as a low pass filter to clean the voltage on V33A further.

    Bead can cause instability, therefore should not be used.
    Too small of resistor will not be effective enough in filtering.
    Too big of a resistor can cause too much of drop in V33A due to current going through and cause premature reset.

    Resistor values between 1 Ohms to 3 Ohms are good.

    Regards,

  • 0 in reply to Yitzhak Bolurian
    Prodigy 10 points

    Hi Yitzhak Bolurian

    Why does bead cause instability?

    Review some paper include TI C2000 and Microchip, it suggested using bead.

    Why is UCD3138 different from the others? How to prove the use of resistor is better?

     

  • 0 in reply to Derek Lo
    TI__Mastermind 18370 points

    The internal circuitry is different in each device/chip, therefore the need for different external components to support proper functionality.

    This is quite similar to the need for different type of engine oil or fuel in different cars.

    The resistor as mentioned in the UCD3138 guideline is matching the proper functionality of UCD3138.

    If the above answers your question, please set the status of this post to resolved.

    Regards,