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

the jitter and 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, place

the capacitors very close to the power-supply terminals and lay out with short loops to minimize inductance. TI

recommends to insert 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 10-1 shows the recommended power supply filtering and decoupling method.

10

F

0.1

F

0.1

F

0.1

F

0.1

F

0.1

F

3.3 V

VDD

10

F

0.1

F

3.3 V

VDDR

2.2

Figure 10-1. Power Supply Decoupling

CDCDB800

SNAS818 – JULY 2021

www.ti.com

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