Chip

Supply

C

0.1 µF

V

CC

Ferrite Bead

C

1 µF

C

10 µF

Board

Supply

CDCVF2310

SCAS666D – JUNE 2001 – REVISED OCTOBER 2015

www.ti.com

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 very low impedance path for high-frequency noise and guards the power supply system

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

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

must be placed very close to the power-supply terminals 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

terminals 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 buffer;

these beads prevent the switching noise from leaking into the board supply. It is imperative to choose an

appropriate ferrite bead with very low DC resistance to provide adequate isolation between the board supply and

the chip supply, as well as to maintain a voltage at the supply terminals that is greater than the minimum voltage

required for proper operation.

Figure 12 shows this recommended power supply decoupling method.

Figure 11. Power Supply Decoupling

14

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