FS6209 ETC-unknow, FS6209 Datasheet - Page 2

• Manufacturer Part Number: FS6209
• Description: Dual Pll Vcxo Clock Generator Ic
• Manufacturer: ETC-unknow

,62 
Table 2: Pin Descriptions
Key: AI = Analog Input; AO = Analog Output; DI = Digital Input; DI
DO = Digital Output; P = Power/Ground; # = Active Low pin
3.0
3.1
The on-chip PLLs are a standard frequency- and phase-
locked loop architecture. The PLL multiplies the reference
oscillator to the desired frequency by a ratio of integers.
The frequency multiplication is exact with a zero synthe-
sis error.
3.2
The VCXO provides a tunable, low-jitter frequency refer-
ence for the rest of the FS6209 system components.
Loading capacitance for the crystal is internal to the
FS6209. No external components (other than the reso-
nator itself) are required for operation of the VCXO.
Continuous fine-tuning of the VCXO frequency is accom-
plished by varying the voltage on the XTUNE pin. The
total change (from one extreme to the other) in effective
loading capacitance is t.b.d. nominal.
The oscillator operates the crystal resonator in the paral-
lel-resonant mode. Crystal warping, or the “pulling” of the
crystal oscillation frequency, is accomplished by altering
the effective load capacitance presented to the crystal by
PIN
1
2
3
4
5
6
7
8
Functional Block Description
Oscillator (VCXO)
Phase-Locked Loop (PLL)
Voltage-Controlled Crystal
TYPE
DO
DO
DO
AO
AI
AI
P
P
XTUNE
NAME
XOUT
CLKA
CLKB
VDD
VSS
VSS
XIN
U
= Input with Internal Pull-Up; DI
VCXO Feedback
Power Supply (+3.3V)
VCXO Tune
Ground
Clock Output A
Clock Output B
Ground
VCXO Drive
2
the oscillator circuit. The actual amount that changing the
load capacitance alters the oscillator frequency will be
dependent on the characteristics of the crystal as well as
the oscillator circuit itself.
Specifically, the motional capacitance of the crystal (usu-
ally referred to by crystal manufacturers as C
capacitance of the crystal (C
(C
the crystal in the oscillator circuit.
A simple formula to obtain the warping capability of a
crystal oscillator is:
where C
load capacitance.
EXAMPLE: A crystal with the following parameters is
used. With C
22.66pF, the coarse tuning range is
D
= Input with Internal Pull-Down; DIO = Digital Input/Output; DI-3 = Three-Level Digital Input,
L
) of the oscillator determine the warping capability of
f
L1
f
(
and C
ppm
0
1
2
DESCRIPTION
.
= 0.02pF, C
02
)
5
L2
are the two extremes of the applied
22
22
2
.
66
.
C
66
C
1
0
= 5pF, C
0
 
10
0
), and the load capacitance
C
5
C
L
2
L
10 6
10
2
    X  T
C
L1
L
= 10pF, and C
C
1
305
0
February 1999
10
C
1
ppm
6
), the static
L
1
.
2.4.99
L2
=