FerriteBead

1 µF

10 µF

0.1 µF

14

CDCLVD1213

SCAS897A – JULY 2010 – REVISED OCTOBER 2016

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10 Power Supply Recommendations

High-performance clock buffers are sensitive to noise on the power supply, which can dramatically increase the

additive jitter of the buffer. Thus, it is essential to reduce noise from the system power supply, especially when

jitter or phase noise is critical to applications.

Filter capacitors are used to eliminate the low-frequency noise from the power supply, where the bypass

capacitors provide the low impedance path for high-frequency noise and guard the power-supply system against

the induced fluctuations. These bypass capacitors also provide instantaneous current surges as required by the

device and must have low equivalent series resistance (ESR). To properly use the bypass capacitors, they must

be placed close to the power-supply pins and laid out with short loops to minimize inductance. TI recommends

adding as many high-frequency (for example, 0.1-µF) bypass capacitors as there are supply pins in the package.

TI recommends, but does not require, inserting a ferrite bead between the board power supply and the chip

power supply that isolates the high-frequency switching noises generated by the clock driver; these beads

prevent the switching noise from leaking into the board supply. Choose an appropriate ferrite bead with low DC-

resistance because it is imperative to provide adequate isolation between the board supply and the chip supply,

as well as to maintain a voltage at the supply pins that is greater than the minimum voltage required for proper

operation.

Figure 18 shows this recommended power-supply decoupling method.

Figure 18. Power-Supply Decoupling