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TLK2711-SP: TLK2711-SP - ferrite bead on power supply.

Shinu.V.Mathew
Genius 10180 points
Part Number: TLK2711-SP

Hi Team,

The datasheet of TLK2711 -SP have a application information that shows the VDDA supply should include a '5 Ohm at 100MHz' ferrite bead but there is no explanation details for this impedance profile for the ferrite bead. In the circuit diagram (Typical Application-fig15) showing the ferrite bead and decoupling capacitors but no supporting notes. Why '5 Ohm at 100MHz'? What if a higher impedance ferrite bead was used,  what would be the effect?

Regards, Shinu Mathew. 

  • 0
    TI__Mastermind 19235 points

    Hi,

    The "'5 Ohm at 100MHz'" figure is not an exact recommended value but rather a suggestion for minimum ferrite bead impedance at that frequency. A larger impedance would provide higher attenuation to the VDDA noise.

    Regards,

    Rodrigo Natal

    HSSC Applications Engineer

  • 0 in reply to Rodrigo Natal
    TI__Genius 10180 points

    Thanks Rodrigo,

    What will be the device dynamic current while operating in 120mhz and 2.5V.

    Can you please share some data.

    Regards, Shinu Mathew. 

  • 0 in reply to Shinu.V.Mathew
    TI__Mastermind 19235 points

    Hi Shinu,

    The typical values from the datasheet still apply for this condition. I unfortunately do not have data to share, as TLK2711-SP is an old legacy product that my product line inherited.

    7.3 Recommended Operating Conditions

    over operating free-air temperature range (unless otherwise noted)

     

     

    MIN     NOM     MAX

    UNIT

     

    VDD           Supply voltage

    Frequency range 1.6 Gbps to 2 Gbps

    2.375         2.5     2.625

     

    V

    Frequency range 1.6 Gbps to 2.5 Gbps

    2.5         2.6         2.7

     

    ICC             Supply current

    Frequency = 1.6 Gbps, PRBS pattern

    110

     

    mA

    Frequency = 2.5 Gbps, PRBS pattern

    160

     

    PD             Power dissipation

    Frequency = 1.6 Gbps, PRBS pattern

    275

     

    mW

    Frequency = 2.5 Gbps, PRBS pattern

    400

    Frequency = 2.5 Gbps, PRBS pattern

    550

     

     

     

     

    Cordially,

    Rodrigo

  • 0 in reply to Rodrigo Natal
    TI__Genius 10180 points

    Thanks Rodrigo.