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CDCLVC1104: Power Supply Decoupling circuit on the datasheet

Oba
Mastermind 18135 points

Part Number: CDCLVC1104
Other Parts Discussed in Thread: CDCV304

Hello

I have two questions about Figure 13. Power Supply Decoupling on CDCLVC1104 datasheet(SCAS895B).
Now I'm also looking to CDCV304. The clock speed is 33MHz.

1)
CVDLVC1104 datasheet recommends to use ferrite beads for power supply decoupling.
But there is no description like that on the CDCV304 datasheet . Why isn't ferrite beads recommended for CDCV304?
What is the difference between CDCLVC1104 and CDCV304 for this recommendation?

2)
3 bypass capacitances, 10uF, 1uF and 0.1uF are put on the Figure 13 circuit of CDCLVC1104 datasheet.
If using only 0.1uF, what kind of problem could happen?

Regards,
Oba

  • 0
    TI__Genius 16845 points
    Hi Oba,

    A1. This recommendation can apply to all clock drivers. Clock drivers produce switching noise which could adversely affect circuit function. Placing a ferrite bead between the clock driver power supply and main board power supply will isolate the noise from going back into your board. It will also isolate noise in the reverse direction. Here is a relevant app note if you are interested: www.ti.com/.../scaa048.pdf

    A2. If you only use the biasing capacitance the DC level on the pin will not be as stable, which can adversely affect device performance. More often, unexpected issues can arise within a system due to insufficient noise filtering (if you do not use the ferrite bead). These system level issues could be difficult to identify.

    Kind regards,
    Lane