84330CI Datasheet, PDF (2/20 Pages) Integrated Device Technology – 720MHz, Low Jitter, Crystal-to-LVPECL Frequency Synthesizer

84330CI Data Sheet
Functional Description
NOTE: The functional description that follows describes operation
using a 16MHz crystal. Valid PLL loop divider values for different
crystal or input frequencies are defined in the Input Frequency
Characteristics, Table 6, NOTE 1.
The 84330CI 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. With a 16MHz
crystal, this provides a 1MHz reference frequency. The VCO of the
PLL operates over a range of 250MHz to 720MHz. The output of the
M divider is also applied to the phase detector.
The phase detector and the M divider force the VCO output fre-
quency 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 84330CI support two input modes
to program the M divider and N output divider. The two input
operational modes are parallel and serial. Figure 1 shows the timing
diagram for each 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 transition on
nP_LOAD or until a serial event occurs. The TEST output is Mode
000 (shift register out) when operating in the parallel input mode.
The relationship between the VCO frequency, the crystal frequency
and the M divider is defined as follows:
fVCO = fXTAL x 2M
16
The M value and the required values of M0 through M8 are shown in
Table 3B, Programmable VCO Frequency Function Table. Valid M
values for which the PLL will achieve lock are defined as 125  M 
360. The frequency out is defined as follows:
fout = fVCO = fXTAL x 2M
N
16
N
Serial operation occurs when nP_LOAD is HIGH and S_LOAD is
LOW. The shift register is loaded by sampling the S_DATA bits with
the rising edge of S_CLOCK. The contents of the shift register are
loaded into the M divider when S_LOAD transitions from
LOW-to-HIGH. The M divide and N output divide values are latched
on the HIGH-to-LOW transition of S_LOAD. If S_LOAD is held
HIGH, data at the S_DATA input is passed directly to the M divider
on each rising edge of S_CLOCK. The serial mode can be used to
program the M and N bits and test bits T2:T0. The internal registers
T2:T0 determine the state of the TEST output as follows in the table
below:
T2
T1
T0 TEST Output
f_OUT
0
0
0 Shift Register Out
f_OUT
0
0
1 HIGH
f_OUT
0
1
0 PLL Reference XTAL ÷16
f_OUT
0
1
1 (VCO ÷ M)/2 (non 50% Duty Cycle M Divider)
f_OUT
1
0
0 f_OUT, LVCMOS Output Frequency < 200MHz
f_OUT
1
0
1 LOW
f_OUT
1
1
0 (S_CLOCK ÷ M)/2 (non 50% Duty Cycle M Divider) S_CLOCK ÷ N Divider
1
1
1 f_OUT ÷ 4
f_OUT
S_CLOCK
SERIAL LOADING
S_DATA
S_LOAD
T2 T1
tt
SH
T0 N1 N0 M8 M7 M6 M5 M4 M3 M2 M1 M0
nP_LOAD
M0:M8, N0:N1
nP_LOAD
nP_LOAD
Figure 1. Parallel & Serial Load Operations
©2016 Integrated Device Technology, Inc
M, N
PARALLEL LOADING
tt
SH
Time
2
t
S
Revision A January 13, 2016