ics8430ay62l Integrated Device Technology, ics8430ay62l Datasheet - Page 12

• Manufacturer Part Number: ics8430ay62l
• Description: Ics8430-62 500mhz, Crystal-to-3.3v, 2.5v Differential Lvpecl Frequency Synthesizer
• Manufacturer: Integrated Device Technology

ICS8430-62 Datasheet
Crystal Input Interface
The ICS8430-62 has been characterized with 18pF parallel resonant
crystals. The capacitor values, C1 and C2, shown in Figure 3 below
were determined using an 18pF parallel resonant crystal and were
chosen to minimize the ppm error. These same capacitor values will
Figure 3. Crystal Input Interface
LVCMOS to XTAL Interface
The XTAL_IN input can accept a single-ended LVCMOS signal
through an AC coupling capacitor. A general interface diagram is
shown in Figure 4. The XTAL_OUT pin can be left floating. The input
edge rate can be as slow as 10ns. For LVCMOS signals, it is
recommended that the amplitude be reduced from full swing to half
swing in order to prevent signal interference with the power rail and
to reduce noise. This configuration requires that the output
Figure 4. General Diagram for LVCMOS Driver to XTAL Input Interface
ICS8430AY-62 REVISION A JULY 2, 2009
18pF Parallel Crystal
V
CC
Ro
X1
Rs
Zo = Ro + Rs
50Ω
C1
22p
C2
22p
XTAL_IN
XTAL_OUT
V
CC
R1
R2
0.1µf
XTAL_IN
XTAL_OUT
12
tune any 18pF parallel resonant crystal over the frequency range and
other parameters specified in this data sheet. The optimum C1 and
C2 values can be slightly adjusted for different board layouts.
impedance of the driver (Ro) plus the series resistance (Rs) equals
the transmission line impedance. In addition, matched termination at
the crystal input will attenuate the signal in half. This can be done in
one of two ways. First, R1 and R2 in parallel should equal the
transmission line impedance. For most 50Ω applications, R1 and R2
can be 100Ω. This can also be accomplished by removing R1 and
making R2 50Ω.
500MHz CRYSTAL-TO-3.3V, 2.5V DIFFERENTIAL LVPECL FREQUENCY SYNTHESIZER
©2009 Integrated Device Technology, Inc.