ICS84330-03 Datasheet, PDF (5/20 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
FUNCTIONAL DESCRIPTION
NOTE: The functional description that follows describes op-
eration using a 16.6667MHz crystal. Valid PLL loop divider
values for different crystal or input frequencies are defined
in the Input Frequency Characteristics, Table 7, NOTE 1.
The ICS84330-03 features a fully integrated PLL and
therefore requires no external components for setting the
loop bandwidth. A quartz crystal is used as the input to the
on-chip oscillator. The output of the oscillator is divided by
16 prior to the phase detector.
The phase detector and the M divider force the VCO output
frequency to be 2M times the reference frequency by
adjusting the VCO control voltage. Note that for some
values of M (either too high or too low), the PLL will not
achieve lock. The output of the VCO is scaled by a divider
prior to being sent to each of the LVPECL output buffers.
The divider provides a 50% output duty cycle.
The programmable features of the ICS84330-03 support
two input modes to program the M divider and N output
divider. The two input operational modes are parallel and
I²C. Figure 1 shows the timing diagram for parallel mode. In
parallel mode the nP_LOAD input is LOW. The data on
inputs M0 through M8 and N0 through N1 is passed
directly to the M divider and N output divider. On the LOW-
to-HIGH transition of the nP_LOAD input, the data is latched
and the M divider remains loaded until the next LOW tran-
sition on nP_LOAD or until an I²C event occurs. The rela-
tionship between the VCO frequency, the crystal frequency
and
the
M
divider
is
defined
as
follows: _fVCO
=
fxtal
16
x
2M
The M value and the required values of M0 through M8 are
shown in Table 3B, Programmable VCO Frequency Func-
tion Table. Valid M values for which the PLL will achieve
lock are defined as 120 ≤ M ≤ 336. The frequency out is
defined
as
follows:
fout
=
fVCO
N
=
fxtal
16
x
2M
N
PARALLEL LOADING
M0:M8, N0:N1
nP_LOAD
M, N
Time
FIGURE 1. PARALLEL LOAD OPERATIONS
84330AY-03
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REV. A FEBRUARY 2, 2006