ICS84330-03 Datasheet, PDF (14/20 Pages) Integrated Circuit Systems – 700MHZ, LOW JITTER, CRYSTAL-TO-3.3V DIFFERENTIAL LVPECL FREQUENCY SYNTHESIZER

Integrated
Circuit
Systems, Inc.
ICS84330-03
700MHZ, LOW JITTER, CRYSTAL-TO-3.3V
DIFFERENTIAL LVPECL FREQUENCY SYNTHESIZER
SPREAD SPECTRUM
Spread-spectrum clocking is a frequency modulation tech-
nique for EMI reduction. When spread-spectrum is enabled,
a 32kHz triangle waveform is used from the nominal 333MHz
clock frequency. An example of a triangle frequency modu-
lation profile is shown in Figure 7A below. The ramp profile
can be expressed as:
• Fnom = Nominal Clock Frequency in Spread OFF mode
(333MHz with 16.6667MHz IN)
• Fm = Nominal Modulation Frequency (32kHz)
• δ = Modulation Factor (0.25% down spread)
It is important to note the ICS84330-03 7dB minimum
spectral reduction is the component-specific EMI reduc-
tion, and will not necessarily be the same as the system
EMI reduction.
(1
-
δ)
fnom
+
2
fm
x
δ
x
fnom
x
t
when
0
<
t
<
2
1
fm
,
(1
-
δ)
fnom
-
2
fm
x
δ
x
fnom
x
t
when ₂
1
fm
<
t
<
1
fm
Fnom
Δ − 10 dBm
B
A
(1 - δ) Fnom
0.5/fm
1/fm
FIGURE 7A. TRIANGLE FREQUENCY MODULATION
δ = 0.25% _➤
➤
FIGURE 7B. 333MHZ CLOCK OUTPUT IN FREQUENCY DOMAIN
(A) SPREAD-SPECTRUM OFF
(B) SPREAD-SPECTRUM ON
84330AY-03
www.icst.com/products/hiperclocks.html
14
REV. A FEBRUARY 2, 2006