REVISION B 5/6/15

84427 DATA SHEET

7

CRYSTAL-TO-LVDS

INTEGRATED FREQUENCY SYNTHESIZER/FANOUT BUFFER

As in any high speed analog circuitry, the power supply

pins are vulnerable to random noise. The 84427 provides

separate power supplies to isolate any high switching

noise from the outputs to the internal PLL.V

individually connected to the power supply plane through vias,

and bypass capacitors should be used for each pin. To achieve

optimum jitter performance, power supply isolation is required.

Figure 1 illustrates how a 24

Ω resistor along with a 10μF and a

.01

μF bypass capacitor should be connected to each V

24

Ω

V

DDA

10

μF

.01

μF

3.3V

.01

μF

V

DD

The 84427 has been characterized with 18pF parallel resonant

crystals. The capacitor values, C1 and C2, shown in Figure 2

below were determined using an 18pF parallel resonant crystal

and were chosen to minimize the ppm error. The optimum C1

and C2 values can be slightly adjusted for different board layouts.

C1

18p

X1

18pF Parallel Crystal

C2

22p

XTAL_IN

XTAL_OUT