ICS840271I

SYNCHRONOUS ETHERNET FREQUENCY TRANSLATOR

7

ICS840271BGI REV. A APRIL 23, 2009

Application Information

Power Supply Filtering Technique

As in any high speed analog circuitry, the power supply pins are

vulnerable to random noise. To achieve optimum jitter perform-

ance, power supply isolation is required. The ICS840271I provides

separate power supplies to isolate any high switching noise from

ly connected to the power supply plane through vias, and 0.01µF

bypass capacitors should be used for each pin. Figure 1 illustrates

an additional 10

Ω resistor along with a 10µF bypass capacitor be

Figure 1. Power Supply Filtering

Wiring the Differential Input to Accept Single Ended Levels

Figure 2 shows how the differential input can be wired to accept

generated by the bias resistors R1, R2 and C1. This bias circuit

should be located as close as possible to the input pin. The ratio of

R1 and R2 might need to be adjusted to position the V_REF in the

center of the input voltage swing. For example, if the input clock

R2/R1 = 0.609.

Figure 2. Single-Ended Signal Driving Differential Input

Recommendations for Unused Input Pins

Inputs:

LVCMOS Control Pins

All control pins have internal pullups or pulldowns; additional

resistance is not required but can be added for additional

protection. A 1k

Ω resistor can be used.

3.3V or 2.5V

10

Ω

10µF

.01µF

.01µF

V_REF

Single Ended Clock Input

CLK

nCLK

R1

1K

C1

0.1u

R2

1K